A Brief History of Microbiology

A Brief History of Microbiology Smallpox: To Be or Not To Be? Smallpox is likely the worst infectious disease of all time, killing an estimated 300 million people in the 19th century alone. It is a terrifying killer, with a death rate as high as 33% and the survivors carrying lifelong scars. British medical doctor Edward Jenner is credited with inventing smallpox vaccination—the world’s first immunization. On May 14, 1796, Jenner collected secretions from a cowpox sore on the hand of a milkmaid and rubbed them into scratches he made on the skin of an eight-yearold boy. Then, about a month later, he injected the boy with secretions from a lesion on a smallpox patient. The child did not get smallpox; he was immune. Jenner termed his technique vaccination, which comes from the Latin term for cow, vacca. Medical doctors began vaccinating people with special two-pronged needles, and eventually smallpox was eradicated worldwide. The last case was documented on October 26, 1977. Eradication represents one of the great triumphs of modern medicine, but smallpox virus itself still exists. Stocks are kept frozen in secure laboratories at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and in the State Research Center of Virology and Biotechnology in Koltsovo, Russia. Imagine you are assigned to be part of a team tasked to determine what to do with the world’s remaining stores of smallpox virus. • Should governments and laboratories keep them? • Or should they be destroyed? In other words, should we intentionally make a species extinct forever? Science is the study of nature that proceeds by posing questions about observations. Why are there seasons? What is the function of the nodules at the base of this plant? Why does this bread taste sour? What does plaque from between teeth look like when magnified? What causes the spread of diseases? Many early written records show that people have always asked questions like these. For example, the Greek physician Hippocrates (ca. 460–ca. 377 b.c.) wondered whether there is a link between environment and disease, and the Greek historian Thucydides (ca. 460–ca. 404 b.c.) questioned why he and other survivors of the plague could have close contact with victims and not fall ill again. For many centuries, the answers to these and other fundamental questions about the nature of life remained largely unanswered. But about 350 years ago, the invention of the microscope began to provide some clues. In this chapter, we’ll see how one man’s determination to answer a fundamental question about the nature of life—What does life really look like?—led to the birth of a new science called microbiology. We’ll then see how the search for answers to other questions—such as those concerning spontaneous generation, the reason fermentation occurs, and the cause of disease—prompted advances in this new science. Finally, we’ll look briefly at some of the key questions microbiologists are asking today. M01_BAUM7206_05_SE_C01.indd 2 Smallpox Viruses • What facts do you need to make an informed decision? • If the decision were to be made today, how would you vote? Go to the study area to solve the problem. The Early Years of Microbiology The early years of microbiology brought the first observations of microbial life and the initial efforts to organize them into logical classifications. What Does Life Really Look Like? LE A R N I N G O UTC O M E S 1.1 Describe the world-changing scientific contributions of Leeuwenhoek. 1.2 Define microbes in the words of Leeuwenhoek and as we know them today. A few people have changed the world of science forever. We’ve all heard of Galileo, Newton, and Einstein, but the list also includes Antoni van Leeuwenhoek (lā′vĕn-huk; 1632–1723), a Dutch tailor, merchant, and lens grinder, and the man who first discovered the bacterial world (FIGURE 1.1). Leeuwenhoek was born in Delft, the Netherlands, and lived most of his 90 years in the city of his birth. What set Leeuwenhoek apart from many other men of his generation was an 12/15/16 11:31 PM       The Early Years of Microbiology Lens ▲ FIGURE 1.1 Antoni van Leeuwenhoek. Leeuwenhoek reported the existence of protozoa in 1674 and of bacteria in 1676. Why did Leeuwenhoek discover protozoa before bacteria? Figure 1.1 Protozoa are generally larger than bacteria. insatiable curiosity coupled with an almost stubborn desire to do everything for himself. His journey to fame began simply enough, when as a cloth merchant he needed to examine the quality of cloth. Rather than merely buying a magnifying lens, he learned to make glass lenses of his own (FIGURE 1.2). Soon he began asking, “What does it really look like?” of everything in his world: the stinger of a bee, the brain of a fly, the leg of a louse, a drop of blood, flakes of his own skin. To find answers, he spent hours examining, reexamining, and recording every detail of each object he observed. Making and looking through his simple microscopes, really no more than magnifying glasses, became the overwhelming passion of his life. His enthusiasm and dedication are evident from the fact that he sometimes personally extracted the metal for a microscope from ore. Further, he often made a new microscope for each specimen, which remained mounted so that he could view it again and again. Then one day, he turned a lens onto a drop of water. We don’t know what he expected to see, but certainly he saw more than he had anticipated. As he reported to the Royal Society of London1 in 1674, he was surprised and delighted by Specimen holder ▲ FIGURE 1.2 Reproduction of Leeuwenhoek’s microscope. This simple device is little more than a magnifying glass with screws for manipulating the specimen, yet with it, Leeuwenhoek changed the way we see our world. The lens, which is convex on both sides, is about the size of a pinhead. The object to be viewed was mounted either directly on the specimen holder or inside a small glass tube, which was then mounted on the specimen holder. Leeuwenhoek had discovered the previously unknown microbial world, which today we know to be populated with tiny animals, fungi, algae, and single-celled protozoa (FIGURE 1.3). In a later report to the Royal Society, he noted that the number of these animals in the plaque of a man’s teeth, are so many that I believe they exceed the number of men in a kingdom. . . . in a quantity of matter no bigger than the 1/100 part of a [grain of] sand. some green streaks, spirally wound serpent-wise, and orderly arranged. . . . Among these there were, besides, very many little animalcules, some were round, while others a bit bigger consisted of an oval. On these last, I saw two little legs near the head, and two little fins at the hind most end of the body. . . . And the motion of most of these animalcules in the water was so swift, and so various, upwards, downwards, and round about, that ’twas wonderful to see.2 1The Royal Society of London for the Promotion of Natural Knowledge, granted a royal charter in 1662, is one of the older and more prestigious scientific groups in Europe. 2Antoni von Leeuwenhoek, in a letter to the Royal Society of London for the Promotion of Natural Knowledge. M01_BAUM7206_05_SE_C01.indd 3 LM 50 μm ▲ FIGURE 1.3 The microbial world. Leeuwenhoek reported seeing a scene very much like this, full of numerous fantastic, cavorting creatures. 11/23/16 2:58 AM 1    A Brief H apter       Ch istory of Microbiology From the figure accompanying his report and the precise description of the size of these organisms from between his teeth, we know that Leeuwenhoek was reporting the existence of bacteria. By the end of the 19th century, Leeuwenhoek’s “beasties,” as he sometimes dubbed them, were called microorganisms, and today we also know them as microbes. Both terms include all organisms that are too small to be seen without a microscope. Because of the quality of his microscopes, his profound observational skills, his detailed reports over a 50-year period, and his report of the discovery of many types of microorganisms, Antoni van Leeuwenhoek was elected to the Royal Society in 1680. He was one of the more famous scientists of his time. Prokaryotic bacterial cells Nucleus of eukaryotic cheek cell How Can Microbes Be Classified? LE A R N I N G O U TC O M E S 1.3 List six groups of microorganisms. 1.4 Explain why protozoa, algae, and nonmicrobial parasitic worms are studied in microbiology. LM 20 μm ▲ FIGURE 1.4 Cells of the bacterium Streptococcus (dark blue) and two human cheek cells. Notice the size difference. 1.5 Differentiate prokaryotic from eukaryotic organisms. Shortly after Leeuwenhoek made his discoveries, the Swedish botanist Carolus Linnaeus (1707–1778) developed a taxonomic system—a system for naming plants and animals and grouping similar organisms together. For instance, Linnaeus and other scientists of the period grouped all organisms into either the animal kingdom or the plant kingdom. Today, biologists still use this basic system, but they have modified Linnaeus’s scheme by adding categories that more realistically reflect the relationships among organisms. For example, scientists no longer classify yeasts, molds, and mushrooms as plants but instead as fungi. (We examine taxonomic schemes in more detail in Chapter 4.) The microorganisms that Leeuwenhoek described can be grouped into six basic categories: bacteria, archaea, fungi, protozoa, algae, and small multicellular animals. The only types of microbes not described by Leeuwenhoek are viruses,3 which are too small to be seen without an electron microscope. We briefly consider organisms in the first five categories in the following sections. Bacteria and Archaea Bacteria and archaea are prokaryotic,4 meaning that their cells lack nuclei; that is, their genes are not surrounded by a membrane. Bacterial cell walls are composed of a polysaccharide called peptidoglycan, though some bacteria lack cell walls. The cell walls of archaea lack peptidoglycan and instead are composed of other chemicals. Members of both groups reproduce asexually. (Chapters 3, 4, and 11 examine other differences viruses are not “organisms,” because they neither replicate themselves nor carry on the chemical reactions of living things. between bacteria and archaea, and Chapters 19–24 discuss pathogenic [disease-causing] bacteria.) Most archaea and bacteria are much smaller than eukaryotic cells (FIGURE 1.4). They live singly or in pairs, chains, or clusters in almost every habitat containing sufficient moisture. Archaea are often found in extreme environments, such as the highly saline and arsenic-rich Mono Lake in California, acidic hot springs in Yellowstone National Park, and oxygen-depleted mud at the bottom of swamps. No archaea are known to cause diseases in humans. Though bacteria may have a poor reputation in our world, the great majority do not cause disease in animals, humans, or crops. Indeed, bacteria are beneficial to us in many ways. For example, without beneficial bacteria, our bodies would be much more susceptible to disease. Also, bacteria (and fungi) degrade dead plants and animals to release phosphorus, sulfur, nitrogen, and carbon back into the air, soil, and water to be used by new generations of organisms. Without microbial recyclers, the world would be buried under the corpses of uncountable dead organisms. Fungi Fungi (fŭn′jī)5 are eukaryotic;6 that is, each of their cells contains a nucleus composed of genetic material surrounded by a distinct membrane. Fungi are different from plants because fungi obtain their food from other organisms (rather than making it for themselves). They differ from animals by having cell walls. 3Technically, Greek pro, meaning “before,” and karyon, meaning “kernel” (which, in this case, refers to the nucleus of a cell). 4From M01_BAUM7206_05_SE_C01.indd 4 5Plural 6From of the Latin fungus, meaning “mushroom.” Greek eu, meaning “true,” and karyon, meaning “kernel.” 11/23/16 2:58 AM Nucleus Spores Pseudopods Budding cell LM (a) (a) SEM 5 μm (b) SEM 200 µm 5 μm ▲ FIGURE 1.5 Fungi. (a) The mold Penicillium chrysogenum, which produces penicillin, has long filaments that intertwine to form its body (not shown). It reproduces by spores. (b) The yeast Saccharomyces cerevisiae. Yeasts are round to oval and typically reproduce by budding. Microscopic fungi include some molds and yeasts. Molds are typically multicellular organisms that grow as long filaments that intertwine to make up the body of the mold. Molds reproduce by sexual and asexual spores, which are cells that produce a new individual without fusing with another cell (FIGURE 1.5a). The cottony growths on cheese, bread, and jams are molds. Penicillium chrysogenum (pen-i-sil′ē-ŭm krī-so′jĕn-ŭm) is a mold that produces penicillin. Yeasts are unicellular and typically oval to round. They reproduce asexually by budding, a process in which a daughter cell grows off the mother cell. Some yeasts also produce sexual spores. An example of a useful yeast is Saccharomyces cere­ visiae (sak-ă-rō-mī’sēz se-ri-vis′ē-ī; FIGURE 1.5b), which causes bread to rise and produces alcohol from sugar (see Beneficial Microbes: Bread, Wine, and Beer on p. 8). Another example of a yeast is Candida albicans (kan′did-ă al′bi-kanz), which causes most cases of yeast infections in women. (Chapters 12 and 19–25 discuss fungi and their significance in the environment, in food production, and as agents of human disease.) Cilia LM (b) 10 µm Flagellum Protozoa Protozoa are single-celled eukaryotes that are similar to animals in their nutritional needs and cellular structure. In fact, protozoa is Greek for “first animals,” though scientists today classify them in their own groups rather than as animals. Most protozoa are capable of locomotion, and one way scientists categorize protozoa is according to their locomotive structures: pseudopods,7 cilia,8 or flagella.9 Pseudopods are extensions of a cell that flow in the direction of travel (FIGURE 1.6a). Cilia are Greek pseudes, meaning “false,” and podos, meaning “foot.” of the Latin cilium, meaning “eyelid.” 9Plural of the Latin flagellum, meaning “whip.” 7Plural 8Plural M01_BAUM7206_05_SE_C01.indd 5 (c) LM 20 µm ▲ FIGURE 1.6 Locomotive structures of protozoa. (a) Pseudopods are cellular extensions used for locomotion and feeding, as seen in Amoeba proteus. (b) Blepharisma americana moves by means of cilia. (c) Flagella are whiplike extensions that are less numerous and longer than cilia, as seen in Peranema. How do cilia and flagella differ? 11/23/16 2:58 AM 1    A Brief H apter       Ch istory of Microbiology (a) LM 10 μm LM (b) 10 μm ▲ FIGURE 1.7 Algae. (a) Spirogyra. These microscopic algae grow as chains of cells containing helical photosynthetic structures. (b) Diatoms. These beautiful algae have glasslike cell walls. numerous short protrusions of a cell that beat rhythmically to propel the protozoan through its environment (FIGURE 1.6b). Flagella are also extensions of a cell but are fewer, longer, and more whiplike than cilia (FIGURE 1.6c). Some protozoa, such as the malaria-causing Plasmodium (plaz-mō′dē-ŭm), are nonmotile in their mature forms. Many protozoa live freely in water, but some live inside animal hosts, where they can cause disease. Most protozoa reproduce asexually, though some are sexual as well. (Chapters 12 and 19–24 further examine protozoa and some diseases they cause.) Other Organisms of Importance to Microbiologists Microbiologists also study parasitic worms, which range in size from microscopic forms (FIGURE 1.8) to adult tapeworms over 10 meters (approximately 33 feet) in length. Even though most parasitic worms are not microscopic as adults, many of them cause diseases that were studied by early microbiologists, so microbiology books and classes often discuss parasitic worms. Further, laboratory scientists diagnose infections of parasitic Red blood cell Algae Algae10 are unicellular or multicellular photosynthetic eukaryotes; that is, like plants, they make their own food from carbon dioxide and water using energy from sunlight. They differ from plants in the relative simplicity of their reproductive structures. Algae are categorized on the basis of their pigmentation and the composition of their cell walls. Large algae, commonly called seaweeds and kelps, are common in the world’s oceans. Manufacturers use gelatinous chemicals from the cell walls of some large algae as thickeners and emulsifiers in many foods and cosmetics. Scientists use the algae-derived chemical called agar to solidify laboratory media. Unicellular algae (FIGURE 1.7) are common in freshwater ponds, streams, and lakes and in the oceans as well. They are the major food of small aquatic and marine animals and provide most of the world’s oxygen as a by-product of photosynthesis. The glasslike cell walls of diatoms provide grit for many polishing compounds. (Chapter 12 discusses other aspects of the biology of algae.) 10Plural LM 30 µm ▲ FIGURE 1.8 An immature stage of a parasitic worm in blood. of the Latin alga, meaning “seaweed.” M01_BAUM7206_05_SE_C01.indd 6 11/23/16 2:58 AM       The Golden Age of Microbiology Virus Bacterium the late 1800s, scientists began to adopt a new philosophy, one that demanded experimental evidence rather than mere acceptance of traditional knowledge. This fresh philosophical foundation, accompanied by improved microscopes, new laboratory techniques, and a drive to answer a series of pivotal questions, propelled microbiology to the forefront as a scientific discipline. TELL ME WHY Some people consider Leeuwenhoek the “Father of Microbiology.” Explain why this moniker makes sense. Viruses assembling inside cell The Golden Age of Microbiology LE A R N I N G O UTC O M E 1.6 List and answer four questions that propelled research in what is called the “Golden Age of Microbiology.” TEM 75 nm ▲ FIGURE 1.9 A colorized electron microscope image of viruses infecting a bacterium. Viruses, which are acellular obligatory parasites, are generally too small to be seen with a light microscope. Notice how small the viruses are compared to the bacterium. worms by finding microscopic eggs and immature stages in blood, fecal, urine, and lymph specimens. (Chapter 23 discusses parasitic worms.) The only type of microbe that remained hidden from Leeuwenhoek and other early microbiologists was the virus, which is typically much smaller than the smallest prokaryote and is not usually visible by light microscopy (FIGURE 1.9). Viruses were not seen until the electron microscope was invented in 1932. All viruses are acellular (not composed of cells) obligatory parasites composed of small amounts of genetic material (either DNA or RNA) surrounded by a protein coat. (Chapter 13 examines the general characteristics of viruses, and Chapters 18–24 discuss specific viral pathogens.) Leeuwenhoek first reported the existence of most types of microorganisms in the late 1600s, but microbiology did not develop significantly as a field of study for almost two centuries. There were a number of reasons for this delay. First, Leeuwenhoek was a suspicious and secretive man. Though he built over 400 microscopes, he never trained an apprentice, and he never sold or gave away a microscope. In fact, he never let anyone—not his family or such distinguished visitors as the czar of Russia—so much as peek through his very best instruments. When Leeuwenhoek died, the secret of creating superior microscopes was lost. It took almost 100 years for scientists to make microscopes of equivalent quality. Another reason that microbiology was slow to develop as a science is that scientists in the 1700s considered microbes to be curiosities of nature and insignificant to human affairs. But in M01_BAUM7206_05_SE_C01.indd 7 For about 50 years, during what is sometimes called the “Golden Age of Microbiology,” scientists and the blossoming field of microbiology were driven by the search for answers to the following four questions: • • • • Is spontaneous generation of microbial life possible? What causes fermentation? What causes disease? How can we prevent infection and disease? Competition among scientists who were striving to be the first to answer these questions drove exploration and discovery in microbiology during the late 1800s and early 1900s. These scientists’ discoveries and the fields of study they initiated continue to shape the course of microbiological research today. In the next sections, we consider these questions and how the great scientists accumulated the experimental evidence that answered them. Does Microbial Life Spontaneously Generate? LE A R N I N G O UTC O M E S 1.7 Identify the scientists who argued in favor of sponta- neous generation. 1.8 Compare and contrast the investigations of Redi, Needham, Spallanzani, and Pasteur concerning spontaneous generation. 1.9 List four steps in the scientific method of investigation. A dry lake bed has lain under the relentless North African desert sun for eight long months. The cracks in the baked, parched mud are wider than a man’s hand. There is no sign of life anywhere in the scorched terrain. With the abruptness characteristic of desert storms, rain falls in a torrent, and a raging flood 11/23/16 2:58 AM 1    A Brief H apter       Ch istory of Microbiology BENEFICIAL MICROBES Bread, Wine, and Beer H H Microorganisms play important roles in people’s lives; for example, pathogens have undeniably altered the course of history. owever, what may be the most important microbiological event—one that has had a greater impact on culture and society than that of any disease or epidemic—was the domestication of the yeast used by bakers and brewers. Its scientific name, Saccharomyces cerevisiae, translates from Latin as “sugar fungus [that makes] beer.” The earliest record of the use of yeast comes from Persia (modern Iran), where archaeologists have found the remains of grapes and wine preservatives in pottery vessels more than 7000 years old. Brewing of beer likely started even earlier, its beginnings undocumented. The earliest examples of leavened bread are from Egypt and show that bread making was routine about 6000 years ago. Before that time, bread was unleavened and flat. It is likely that making wine and brewing beer occurred earlier than the use of leavened bread because Saccharomyces is naturally found on grapes, which can begin to ferment while still on the vine. istorians hypothesize that early bakers may have exposed bread dough to circulating air, hoping that the invisible and inexplicable of roiling water and mud crashes down the dry streambed and fills the lake. Within hours, what had been a lifeless, dry mudflat becomes a pool of water teeming with billions of shrimp; by the next day it is home to hundreds of toads. Where did these animals come from? Many philosophers and scientists of past ages thought that living things arose via three processes: through asexual reproduction, through sexual reproduction, or from nonliving matter. The appearance of shrimp and toads in the mud of what so recently was a dry lake bed was seen as an example of the third process, which came to be known as abiogenesis,11 or spontaneous generation. The theory of spontaneous generation as promulgated by Aristotle (384–322 b.c.) was widely accepted for over 2000 years because it seemed to explain a variety of commonly observed phenomena, such as the appearance of maggots on spoiling meat. However, the validity of the theory came under challenge in the 17th century. Redi’s Experiments In the late 1600s, the Italian physician Francesco Redi (1626– 1697) demonstrated by a series of experiments that when decaying meat was kept isolated from flies, maggots never developed, whereas meat exposed to flies was soon infested with maggots (FIGURE 1.10). As a result of experiments such as these, scientists began to doubt Aristotle’s theory and adopt the view that animals come only from other animals. 11From Greek a, meaning “not”; bios, meaning “life”; and genein, meaning “to produce.” M01_BAUM7206_05_SE_C01.indd 8 “fermentation principle” would inoculate the bread. Another hypothesis is that bakers learned to add small amounts of beer or wine to the bread, intentionally inoculating the dough with yeast. Of course, all those years before Leeuwenhoek and Pasteur, no one knew that the fermenting ingredient of wine was a living organism. Besides its role in baking and in making alcoholic beverages, S. cerevisiae is an important tool for the study of cells. Scientists use yeast to delve into the mysteries of cellular function, organization, and genetics, making Saccharomyces the most intensely studied eukaryote. In fact, molecular biologists published the complete sequence of the genes of S. cerevisiae in 1996—the first complete sequence published for any eukaryotic cell. Today, scientists are working toward using S. cerevisiae in novel ways. For example, some nutritionists and gastroenterologists are examining the use of Saccharomyces as a probiotic, that is, a microorganism intentionally taken to ward off disease and promote good health. Research suggests that the yeast helps treat diarrhea and colitis and may even help prevent these and other gastrointestinal diseases. Flask unsealed Flask sealed Flask covered with gauze ▲ FIGURE 1.10 Redi’s experiments. When the flask remained unsealed, maggots covered the meat within a few days. When the flask was sealed, flies were kept away, and no maggots appeared on the meat. When the flask opening was covered with gauze, flies were kept away, and no maggots appeared on the meat, although a few maggots appeared on top of the gauze. Needham’s Experiments The debate over spontaneous generation was rekindled when Leeuwenhoek discovered microbes and showed that they appeared after a few days in freshly collected rainwater. Though scientists agreed that larger animals could not arise spontaneously, they disagreed about Leeuwenhoek’s “wee animalcules”; surely they did not have parents, did they? They must arise spontaneously. The proponents of spontaneous generation pointed to the careful demonstrations of British investigator John T. Needham 11/23/16 2:58 AM       The Golden Age of Microbiology (1713–1781). He boiled beef gravy and infusions12 of plant material in vials, which he then tightly sealed with corks. Some days later, Needham observed that the vials were cloudy, and examination revealed an abundance of “microscopical animals of most dimensions.” As he explained it, there must be a “life force” that causes inanimate matter to spontaneously come to life because he had heated the vials sufficiently to kill everything. Needham’s experiments so impressed the Royal Society that they elected him a member. Spallanzani’s Experiments Then, in 1799, the Italian Catholic priest and scientist Lazzaro Spallanzani (1729–1799) reported results that contradicted Needham’s findings. Spallanzani boiled infusions for almost an hour and sealed the vials by melting their slender necks closed. His infusions remained clear unless he broke the seal and exposed the infusion to air, after which they became cloudy with microorganisms. He concluded three things: • Needham either had failed to heat his vials sufficiently to kill all microbes or had not sealed them tightly enough. • Microorganisms exist in the air and can contaminate experiments. • Spontaneous generation of microorganisms does not occur; all living things arise from other living things. Although Spallanzani’s experiments would appear to have settled the controversy once and for all, it proved difficult to dethrone a theory that had held sway for 2000 years, especially when so notable a man as Aristotle had propounded it. One of the criticisms of Spallanzani’s work was that his sealed vials did not allow enough air for organisms to thrive; another objection was that his prolonged heating destroyed the “life force.” The debate continued until the French chemist Louis Pasteur (FIGURE 1.11) conducted experiments that finally laid the theory of spontaneous generation to rest. Pasteur’s Experiments Louis Pasteur (1822–1895) was an indefatigable worker who pushed himself as hard as he pushed others. As he wrote his sisters, “To will is a great thing dear sisters, for Action and Work usually follow Will, and almost always Work is accompanied by Success. These three things, Work, Will, Success, fill human existence. Will opens the door to success both brilliant and happy; Work passes these doors, and at the end of the journey Success comes to crown one’s efforts.” When his wife complained about his long hours in the laboratory, he replied, “I will lead you to fame.” Pasteur’s determination and hard work are apparent in his investigations of spontaneous generation. Like Spallanzani, he boiled infusions long enough to kill everything. But instead of sealing the flasks, he bent their necks into an S-shape, which allowed air to enter while preventing the introduction of dust and microbes into the broth (FIGURE 1.12). ▲ FIGURE 1.11 Louis Pasteur. Often called the Father of Microbiology, he disproved spontaneous generation. In this depiction, Pasteur examines some bacterial cultures. Crowded for space and lacking funds, he improvised an incubator in the opening under a staircase. Day after day, he crawled on hands and knees into this incommodious space and examined his flasks for the cloudiness that would indicate the presence of living organisms. In 1861, he reported that his “swan-necked flasks” remained free of microbes even 18 months later. Because the flasks contained all the nutrients (including air) known to be required by living things, he concluded, “Never will spontaneous generation recover from the mortal blow of this simple experiment.” Pasteur followed this experiment with demonstrations that microbes in the air were the “parents” of Needham’s microorganisms. He broke the necks off some flasks, exposing the liquid in them directly to the air, and he carefully tilted others so that the liquid touched the dust that had accumulated in their necks. The next day, all of these flasks were cloudy with microbes. He concluded that the microbes in the liquid were the progeny of microbes that had been on the dust particles in the air. The Scientific Method The debate over spontaneous generation led in part to the development of a generalized scientific method by which questions are answered through observations of the outcomes of carefully controlled experiments instead of by conjecture or according to the opinions of any authority figure. The scientific method, which provides a framework for conducting an investigation rather than a rigid set of specific “rules,” consists of four basic steps (FIGURE 1.13): 1 2 3 4 12Infusions are broths made by heating water containing plant or animal material. M01_BAUM7206_05_SE_C01.indd 9 A group of observations leads a scientist to ask a question about some phenomenon. The scientist generates a hypothesis—that is, a potential answer to the question. The scientist designs and conducts an experiment to test the hypothesis. Based on the observed results of the experiment, the scientist either accepts, rejects, or modifies the hypothesis. 11/23/16 2:58 AM H 1    A Brief apter       Ch istory of Microbiology Steam escapes from open end of flask. Dust from air settles in bend. Air moves in and out of flask. Months Boil infusion. Infusion sits; no microbes appear. Infusion remains sterile indefinitely. ▲ FIGURE 1.12 Pasteur’s experiments with “swan-necked flasks.” As long as the flask remained upright, no microbial growth appeared in the infusion. The scientist then returns to earlier steps in the method, either modifying hypotheses and then testing them or repeatedly testing accepted hypotheses until the evidence for a hypothesis is convincing. Accepted hypotheses that explain many observations and are repeatedly verified by numerous scientists over many years are called theories or laws. Note that for the scientific community to accept experiments (and their results) as valid, they must include appropriate control groups—groups that are treated exactly the same as the other groups in the experiment except for the one variable that the experiment is designed to test. In Pasteur’s experiments on spontaneous generation, for example, his “control flasks” were the sterile infusion composed of all the nutrients living things need as well as air made available through the flasks’ “swan necks.” His “experimental flasks” for testing his hypothesis were exposed to exactly the same conditions plus contact with the dust in the bend in the neck. Because exposure to the dust was the only difference between the control and experimental groups, Pasteur was able to conclude that the microbes growing in the infusion arrived on the dust particles. What Causes Fermentation? LE A R N I N G O UTC O M E S 1.10 Discuss the significance of Pasteur’s fermentation experi- ments to our world today. 1.11 Explain why Pasteur may be considered the Father of Microbiology. 1.12 Identify the scientist whose experiments led to the field of biochemistry and the study of metabolism. The controversy over spontaneous generation was largely a philosophical exercise among men who conducted research to gain basic scientific knowledge and not to apply the knowledge they gained. However, the second question that moved microbial studies forward in the 1800s had tremendous practical applications. Observations 1 2 Hypothesis Experimental data support hypothesis Repeat 3 Experiment, including control groups 4 Experimental data do not support hypothesis Theory or law Reject hypothesis Modify hypothesis V Tu tor Modified experiment Observations Accept hypothesis ideo Question ▲ FIGURE 1.13 The scientific method, which forms a framework for scientific research. M01_BAUM7206_05_SE_C01.indd 10 11/23/16 2:58 AM Observation: Fermenting grape juice Hypothesis Microscopic analysis shows juice contains yeasts and bacteria. Experiment Day 1: Flasks of grape juice are heated sufficiently to kill all microbes. I. Spontaneous fermentation occurs. II. Air ferments grape juice. III. Bacteria ferment grape juice into alcohol. IV. Yeasts ferment grape juice into alcohol. Observation Conclusion Day 2 Flask is sealed. Flask remains open to air via curved neck. Juice in flask is inoculated with bacteria and sealed. Juice in flask is inoculated with yeast and sealed. No fermentation; juice remains free of microbes. Reject hypothesis I. No fermentation; juice remains free of microbes. Reject hypothesis II. Bacteria reproduce; acids are produced. Modify hypothesis III; bacteria ferment grape juice into acids. Yeasts reproduce; alcohol is produced. Accept hypothesis IV; yeasts ferment grape juice into alcohol. ▲ FIGURE 1.14 How Pasteur applied the scientific method in investigating the nature of fermentation. After observing that fermenting grape juice contained both yeasts and bacteria, Pasteur hypothesized that these organisms cause fermentation. On eliminating the possibility that fermentation could occur spontaneously or be caused by air (hypotheses I and II), he concluded that fermentation requires the presence of living cells. The results of additional experiments (those testing hypotheses III and IV) indicated that bacteria ferment grape juice to produce acids and that yeasts ferment grape juice to produce alcohol. Which of Pasteur’s flasks was the control? Figure 1.14 The sealed flask that remained free of microorganisms served as the control. Our story resumes in 19th-century France, where spoiled, acidic wine was threatening the livelihood of many grape growers. This led to a fundamental question, “What causes the fermentation of grape juice into wine?” This question was so important to vintners that they funded research concerning fermentation, hoping scientists could develop methods to promote the production of alcohol and prevent spoilage by acid during fermentation. Pasteur’s Experiments Scientists of the 1800s used the word fermentation to mean not only the formation of alcohol from sugar but also other chemical reactions, such as the formation of lactic acid, the putrefaction of meat, and the decomposition of waste. Many scientists asserted that air caused fermentation reactions; others insisted that living organisms were responsible. The debate over the cause of fermentation reactions was linked to the debate over spontaneous generation. Some scientists proposed that the yeasts observed in fermenting juices M01_BAUM7206_05_SE_C01.indd 11 were nonliving globules of chemicals and gases. Others thought that yeasts were alive and were spontaneously generated during fermentation. Still others asserted that yeasts not only were living organisms but also caused fermentation. Pasteur conducted a series of careful observations and experiments that answered the question, “What causes fermentation?” First, he observed yeast cells growing and budding in grape juice and conducted experiments showing that they arise only from other yeast cells. Then, by sealing some sterile flasks containing grape juice and yeast and by leaving others open to the air, he demonstrated that yeast could grow with or without oxygen; that is, he discovered that yeasts are facultative anaerobes13—organisms that can live with or without oxygen. Finally, by introducing bacteria and yeast cells into different flasks of sterile grape juice, he proved that bacteria ferment grape juice to produce acids and that yeast cells ferment grape juice to produce alcohol (FIGURE 1.14). 13From Greek an, meaning “not”; aer, meaning “air” (i.e., oxygen); and bios, meaning “life.” 11/23/16 2:58 AM 1    A Brief H apter       Ch istory of Microbiology TABLE 1.1 Some Industrial Uses of Microbes Buchner’s Experiments Cheese Flavoring and ripening produced by bacteria and fungi; flavors dependent on the source of milk and the type of microorganism Alcoholic beverages Alcohol produced by bacteria or yeast by fermentation of sugars in fruit juice or grain Soy sauce Produced by fungal fermentation of soybeans Vinegar Produced by bacterial fermentation of sugar Yogurt Produced by certain bacteria growing in milk Sour cream Produced by bacteria growing in cream Artificial sweetener Amino acids synthesized by bacteria from sugar Studies on fermentation began with the idea that fermentation reactions were strictly chemical and did not involve living organisms. This idea was supplanted by Pasteur’s work showing that fermentation proceeded only when living cells were present and that different types of microorganisms growing under varied conditions produced different end products. In 1897, the German scientist Eduard Buchner (1860–1917) resurrected the chemical explanation by showing that fermentation does not require living cells. Buchner’s experiments demonstrated the presence of enzymes, which are cell-produced proteins that promote chemical reactions. Buchner’s work began the field of biochemistry and the study of metabolism, a term that refers to the sum of all chemical reactions within an organism. Bread Rising of dough produced by action of yeast; sourdough results from bacteria-produced acids What Causes Disease? Product or Process Contribution of Microorganism Foods and Beverages Other Products LE A R N I N G O UTC O M E S Produced by bacteria and fungi uman growth hormone, human insulin Produced by genetically engineered bacteria 1.13 List at least seven contributions made by Koch to the Laundry enzymes Isolated from bacteria 1.14 List the four steps that must be taken to prove the cause Vitamins Isolated from bacteria Diatomaceous earth (in polishes and buffing compounds) Composed of cell walls of microscopic algae Pest control chemicals Insect pests killed or inhibited by insectdestroying bacteria Drain opener Protein-digesting and fat-digesting enzymes produced by bacteria H Antibiotics Pasteur’s discovery that anaerobic bacteria fermented grape juice into acids suggested a method for preventing the spoilage of wine. His name became a household word when he developed pasteurization, a process of heating the grape juice just enough to kill most contaminating bacteria without changing the juice’s basic qualities. After pasteurization, wine makers added yeast to ensure that alcohol fermentation occurred. Pasteur thus began the field of industrial microbiology (or biotechnology), in which microbes are intentionally used to manufacture products (TABLE 1.1; see also Chapter 25). Today, pasteurization is used routinely on milk to eliminate pathogens that cause such diseases as bovine tuberculosis and brucellosis; it is also used to eliminate pathogens in juices and other beverages. These are just a few of the many experiments Pasteur conducted with microbes. Although a few of Pasteur’s successes can be attributed to the superior microscopes available in the late 1800s, his genius is clearly evident in his carefully designed and straightforward experiments. Because of his many, varied, and significant accomplishments in working with microbes, Pasteur may be considered the Father of Microbiology. M01_BAUM7206_05_SE_C01.indd 12 field of microbiology. of an infectious disease. 1.15 Describe the contribution of Gram to the field of microbiology. You are a physician in London, and it is August 1854. It is past midnight, and you have been visiting patients since before dawn. As you enter the room of your next patient, you observe with frustration and despair that this case is like hundreds of others you and your colleagues have attended in the neighborhood over the past month. A five-year-old boy with a vacant stare lies in bed listlessly. As you watch, he is suddenly gripped by severe abdominal cramps, and his gastrointestinal tract empties in an explosion of watery diarrhea. The voided fluid is clear, colorless, odorless, and streaked with thin flecks of white mucus, reminiscent of water poured off a pot of cooking rice. His anxious mother changes his bedclothes as his father gives him a sip of water, but it is of little use. With a heavy heart, you confirm the parents’ fear—their child has cholera, and there is nothing you can do. He will likely die before morning. As you despondently turn to go, the question that has haunted you for two months is foremost in your mind: What causes such a disease? The third question that propelled the advance of microbiology concerned disease, defined generally as any abnormal condition in the body. Prior to the 1800s, disease was attributed to various factors, including evil spirits, astrological signs, imbalances in body fluids, and foul vapors. Although the Italian philosopher Girolamo Fracastoro (1478–1553) conjectured as early as 1546 that “germs14 of contagion” cause disease, the idea that germs might be invisible living organisms awaited Leeuwenhoek’s investigations 130 years later. 14From Latin germen, meaning “sprout.” 11/23/16 2:58 AM       The Golden Age of Microbiology ▲ FIGURE 1.15 Robert Koch. Koch was instrumental in modifying the scientific method to prove that a given pathogen caused a specific disease. Pasteur’s discovery that bacteria are responsible for spoiling wine led naturally to his hypothesis in 1857 that microorganisms are also responsible for diseases. This idea came to be known as the germ theory of disease. Because a particular disease is typically accompanied by the same symptoms in all affected individuals, early investigators suspected that diseases such as cholera, tuberculosis, and anthrax are each caused by a specific germ, called a pathogen.15 Today, we know that some diseases are genetic and that allergic reactions and environmental toxins cause others, so the germ theory applies only to infectious16 diseases. Just as Pasteur was the chief investigator in disproving spontaneous generation and determining the cause of fermentation, so Robert Koch (1843–1910) dominated etiology17 (disease causation) (FIGURE 1.15). Koch’s Experiments Koch was a country doctor in Germany when he began a race with Pasteur to discover the cause of anthrax, which is a potentially fatal disease, primarily of animals, in which toxins produce ulceration of the skin. Anthrax, which can spread to humans, caused untold financial losses to farmers and ranchers in the 1800s. Koch carefully examined the blood of infected animals, and in every case he identified rod-shaped bacteria18 in chains. He observed the formation of resting stages (endospores) within the bacterial cells and showed that the endospores always produced anthrax when they were injected into mice. This was the first time that a bacterium was proven to cause a disease. Koch published his findings in 1876. As a result of his successful work on anthrax, Koch moved to Berlin and was given facilities and funding to continue his research. Heartened by his success, Koch turned his attention to other diseases. He had been fortunate when he chose anthrax Greek pathos, meaning “disease,” and genein, meaning “to produce.” Latin inficere, meaning “to taint” (i.e., with a pathogen). 17 From Greek aitia, meaning “cause,” and logos, meaning “word” or “study.” 18Now known as Bacillus anthracis—Latin for “the rod of anthrax.” 15From 16From M01_BAUM7206_05_SE_C01.indd 13 for his initial investigations, because anthrax bacteria are quite large and easily identified with the microscopes of that time. However, most bacteria are very small, and different types exhibit few or no visible differences. Koch was puzzled regarding how he was to distinguish among these bacteria. He solved the problem by taking specimens (e.g., blood, pus, or sputum) from disease victims and then smearing the specimens onto a solid surface such as a slice of potato or a gelatin medium. He then waited for bacteria and fungi present in the specimen to multiply and form distinct colonies (FIGURE 1.16). Koch hypothesized that each colony consisted of the progeny of a single cell. He then inoculated samples from each colony into laboratory animals to see which caused disease. Koch’s method of isolation is a standard technique in microbiological and medical labs to this day, though agar derived from red algae is used instead of gelatin or potato. Koch and his colleagues are also responsible for many other advances in laboratory microbiology, including the following: • • • • • • • • Simple staining techniques for bacterial cells and flagella The first photomicrograph of bacteria The first photograph of bacteria in diseased tissue Techniques for estimating the number of bacteria in a solution based on the number of colonies that form after inoculation onto a solid surface The use of steam to sterilize growth media The use of Petri19 dishes to hold solid growth media Laboratory techniques such as transferring bacteria between media using a metal wire that has been heat-sterilized in a flame Elucidation of bacteria as distinct species Koch’s Postulates After discovering the anthrax bacterium, Koch continued to search for disease agents. In two pivotal scientific publications in 1882 and 1884, he announced that the cause of tuberculosis was a rod-shaped bacterium, Mycobacterium tuberculosis (mī′kōbak-tēr′ē-ŭm too-ber-kyū-lō′sis). In 1905, he received the Nobel Prize in Physiology or Medicine for this work. In his publications on tuberculosis, Koch elucidated a series of steps that must be taken to prove the cause of any infectious disease. These steps, now known as Koch’s postulates, are one of his important contributions to microbiology. His postulates (which we discuss in more detail in Chapter 14) are the following: 1. The suspected causative agent must be found in every case of the disease and be absent from healthy hosts. 2. The agent must be isolated and grown outside the host. 3. When the agent is introduced to a healthy, susceptible host, the host should get the disease. 4. The same agent must be found in the diseased experimental host. 19Named for Richard Petri, Koch’s coworker, who invented them in 1887. 11/23/16 2:58 AM H 1    A Brief apter       Ch istory of Microbiology Bacterium 6 Bacterium 5 Bacterium 7 Bacterium 4 Bacterium 3 Bacterium 8 Bacterium 9 Bacterium 10 Bacterium 11 Bacterium 2 Bacterium 1 Bacterium 12 ▲ FIGURE 1.16 Bacterial colonies on a solid surface (agar). Differences in colony shape, size, and color indicate the presence of different species (twelve are labeled). Such differences allowed Koch to isolate specific types of bacteria that could be tested for their ability to cause diseases. We use the term suspected causative agent because it is merely “suspected” until the postulates have been fulfilled, and “agent” can refer to any fungus, protozoan, bacterium, virus, or other pathogen. There are practical and ethical limits in the application of Koch’s postulates, but in almost every case they must be satisfied before the cause of an infectious disease is proven. During microbiology’s Golden Age, other scientists used Koch’s postulates and laboratory techniques introduced by Koch and Pasteur to discover the causes of most protozoan and bacterial diseases as well as some viral diseases. For example, Charles Laveran (1845–1922) showed that a protozoan is the cause of malaria, and Edwin Klebs (1834–1913) described the bacterium that causes diphtheria. Dmitri Ivanovsky (1864–1920) and Martinus Beijerinck (1851–1931) discovered that a certain disease in tobacco plants is caused by a pathogen that passes through filters with such extremely small pores that bacteria cannot pass through. Beijerinck, recognizing that the pathogen was not bacterial, called it a filterable virus. Now such pathogens are simply called viruses. As previously noted, viruses could not be seen until electron microscopes were invented in 1932. The American physician Walter Reed (1851–1902) proved in 1900 that viruses can cause such diseases as yellow fever in humans. (Chapter 13 deals with virology, and Chapters 18–24 deal with viral diseases.) A partial list of scientists and the pathogens they discovered is provided in TABLE 1.2. Though Koch reported a simple staining technique in 1877, the Danish scientist Hans Christian Gram (1853–1938) developed a more important staining technique in 1884. His procedure, which involves the application of a series of dyes, leaves some microbes purple and others pink. We now label the purple cells as Gram positive and the pink ones as Gram negative, and we use the Gram procedure to separate bacteria into these two large groups (FIGURE 1.17). Gram-positive Gram-negative Gram’s Stain The first of Koch’s postulates demands that the suspected agent be found in every case of a given disease, which presupposes that minute microbes can be seen and identified. However, because most microbes are colorless and difficult to see, scientists began to use dyes to stain them and make them more visible under the microscope. M01_BAUM7206_05_SE_C01.indd 14 LM 20 µm ▲ FIGURE 1.17 Results of Gram staining. Gram-positive cells (in this case, Staphylococcus aureus) are purple; Gram-negative cells (in this case, Escherichia coli) are pink. 11/23/16 2:58 AM       The Golden Age of Microbiology TABLE 1.2 Other Notable Scientists of the Golden Age of Microbiology and the Agents of Disease They Discovered Scientist Year Disease Agent Edwin Klebs 1883 Diphtheria Corynebacterium diphtheriae (bacterium) Theodor Escherich 1884 Travelers' diarrhea; bladder infections Escherichia coli (bacterium) Albert Fraenkel 1884 Pneumonia Streptococcus pneumoniae (bacterium) David Bruce 1887 Undulant fever (brucellosis) Brucella melitensis (bacterium) Anton Weichselbaum 1887 Meningococcal meningitis Neisseria meningitidis (bacterium) A. A. Gartner 1888 Salmonellosis (form of food poisoning) Salmonella species (bacterium) Shibasaburo Kitasato 1889 Tetanus Clostridium tetani (bacterium) Dmitri Ivanovsky and 1892 Tobacco mosaic disease Tobamovirus tobacco mosaic virus Martinus Beijerinck 1898 William Welch and George Nuttall 1892 Gas gangrene Clostridium perfringens (bacterium) Alexandre Yersin and Shibasaburo Kitasato 1894 Bubonic plague Yersinia pestis (bacterium) Kiyoshi Shiga 1898 Shigellosis (a type of severe diarrhea) Shigella dysenteriae (bacterium) Walter Reed 1900 Yellow fever Flavivirus yellow fever virus Robert Forde and Joseph Dutton 1902 African sleeping sickness Trypanosoma brucei gambiense (protozoan) The Gram stain is still the most widely used staining technique. It is one of the first steps carried out when bacteria are being identified, and it is one of the procedures you will learn in microbiology lab. (Chapter 4 discusses the full procedure.) How Can We Prevent Infection and Disease? LE A R N I N G O U TC O M E S 1.16 Identify six health care practitioners who did pioneering research in the areas of public health microbiology and epidemiology. 1.17 Name two scientists whose work with vaccines began the field of immunology. 1.18 Describe the quest for a “magic bullet.” The last great question that drove microbiological research during the Golden Age was how to prevent infectious diseases. Though some methods of preventing or limiting disease were discovered even before it was understood that microorganisms caused contagious diseases, great advances occurred after Pasteur and Koch showed that life comes from life and that microorganisms can cause diseases. In the mid-1800s, modern principles of hygiene, such as those involving sewage and water treatment, personal cleanliness, and pest control, were not widely practiced. Typically, medical personnel and health care facilities lacked adequate cleanliness. Healthcare-associated infections (HAI), formerly M01_BAUM7206_05_SE_C01.indd 15 called nosocomial20 infections, were rampant. For example, surgical patients frequently succumbed to gangrene acquired while under their doctor’s care, and many women who gave birth in hospitals died from puerperal 21 fever. Six health care practitioners who were especially instrumental in changing health care delivery methods were Ignaz Semmelweis, Joseph Lister, Florence Nightingale, John Snow, Edward Jenner, and Paul Ehrlich. Semmelweis and Handwashing Ignaz Semmelweis (1818–1865) was a physician on the obstetric ward of a teaching hospital in Vienna. In about 1848, he observed that women giving birth in the wing where medical students were trained died from puerperal fever at a rate 20 times higher than the mortality rates of either women attended by midwives in an adjoining wing or women who gave birth at home. Though Pasteur had not yet elaborated his germ theory of disease, Semmelweis hypothesized that medical students carried “cadaver particles” from their autopsy studies into the delivery rooms and that these “particles” resulted in puerperal fever. Semmelweis gained support for his hypothesis when a doctor who sliced his finger during an autopsy died after showing symptoms similar to those of puerperal fever. Today, we know that the primary cause of puerperal fever is a bacterium in the genus Streptococcus (strep-tō-kok′ŭs; see Figure 1.4), which Greek nosos, meaning “disease,” and komein, meaning “to care for” (relating to a hospital). 21From Latin puerperus, meaning “childbirth.” 20From 06/03/2018 06:59 CLINICAL CASE STUDY 1    A Brief H apter       Ch istory of Microbiology Remedy for Fever or Prescription for Death? Victims suffered from high fever, nausea, skin eruptions, black vomit, and jaundice. The treatment for yellow fever in the 18th century was often worse than the disease: physicians administered potions to purge the victims’ intestines and drained up to four-fifths of their patients’ blood in the mistaken belief the bloodletting would stem fever. These attempted remedies often left patients tired, weak, and unable to fight the virus. Without effective treatments, the epidemic stopped only when the first frost arrived. H U In the late 18th century, Philadelphia was one of the larger and wealthier cities in the nited States and served as the capital. That changed in 1793. The city had an unusually wet spring, which left behind stagnant pools that became breeding grounds for mosquitoes. At about the same time, refugees from the slave revolution in aiti fled to Philadelphia, carrying the yellow fever virus. In late August 1793, a female Aedes aegypti mosquito bit an infected refugee and then bit a healthy Philadelphian. This began a yellow fever epidemic that killed 10% of the city’s population within three months and led another 30% to flee for their lives. is usually harmless on the skin or in the mouth but causes severe complications when it enters the blood. Semmelweis began requiring medical students to wash their hands with chlorinated lime water, a substance long used to eliminate the smell of cadavers. Mortality in the subsequent year dropped from 18.3% to 1.3%. Despite his success, Semmelweis was ridiculed by the director of the hospital and eventually was forced to leave. He returned to his native Hungary, where his insistence on handwashing met with general approval when it continued to produce higher patient survival rates. Though his impressive record made it easier for later doctors to institute changes, Semmelweis was unsuccessful in gaining support for his method from most European doctors. He became severely depressed and was committed to a mental hospital, where he died from an infection of Streptococcus, the very organism he had fought for so long. 1. People who left the city seemed to have milder cases of yellow fever or avoided the infection altogether. Explain why. 2. The story mentions that the coming of the first frost brought an end to the epidemic. Discuss the possible reasons why this would provide at least temporary relief from the epidemic. Nightingale and Nursing Florence Nightingale (1820–1910) (FIGURE 1.18) was a dedicated English nurse who introduced cleanliness and other antiseptic techniques into nursing practice. She was instrumental in setting standards of hygiene that saved innumerable lives during the Crimean War of 1854–1856. One of her first requisitions in the military hospital was for 200 scrubbing brushes, which she and her assistants used diligently in the squalid wards. She next arranged for each patient’s filthy clothes and Lister’s Antiseptic Technique Shortly after Semmelweis was rejected in Vienna, the English physician Joseph Lister (1827–1912) modified and advanced the idea of antisepsis22 in health care settings. As a surgeon, Lister was aware of the dreadful consequences that resulted from the infection of wounds. Therefore, he began spraying wounds, surgical incisions, and dressings with carbolic acid (phenol), a chemical that had previously proven effective in reducing odor and decay in sewage. Like Semmelweis, he initially met with some resistance, but when he showed that it reduced deaths among his patients by two-thirds, his method was accepted into common practice. In this manner, Lister vindicated Semmelweis, became the founder of antiseptic surgery, and opened new fields of research into antisepsis and disinfection. 22From Greek anti, meaning “against,” and sepein, meaning “putrefaction.” M01_BAUM7206_05_SE_C01.indd 16 ▲ FIGURE 1.18 Florence Nightingale. The founder of modern nursing, she was influential in introducing antiseptic technique into nursing practice. 11/23/16 2:58 AM       The Modern Age of Microbiology dressings to be replaced or cleaned at a different location, thus removing many sources of infection. She thoroughly documented statistical comparisons to show that poor food and unsanitary conditions in the hospitals were responsible for the deaths of many soldiers. After the war, Nightingale returned to England, where she actively exerted political pressure to reform hospitals and implement public health policies. Perhaps her greatest achievements were in nursing education. For example, she founded the Nightingale School for Nurses—the first of its kind in the world. Snow and Epidemiology Another English physician, John Snow (1813–1858), also played a key role in setting standards for good public hygiene to prevent the spread of infectious diseases. Snow had been studying the propagation of cholera and suspected that the disease was spread by a contaminating agent in water. In 1854, he mapped the occurrence of cholera cases during an epidemic in London and showed that they centered around a public water supply on Broad Street. Though Snow did not know the cause of cholera, his careful documentation of the epidemic highlighted the critical need for adequate sewage treatment and a pure water supply. His study was the foundation for two branches of microbiology—infection control and epidemiology,23 which is the study of the occurrence, distribution, and spread of disease in humans. Jenner’s Vaccine In 1796, the English physician Edward Jenner (1749–1823) tested the hypothesis that a mild disease called cowpox provided protection against potentially fatal smallpox. After he intentionally inoculated a boy with pus collected from a milkmaid’s cowpox lesion, the boy developed cowpox and survived. When Jenner then infected the boy with smallpox pus, he found that the boy had become immune24 to smallpox. (Today, experiments that intentionally expose human subjects to deadly pathogens are unethical.) In 1798, Jenner reported similar results from additional experiments, demonstrating the validity of the procedure he named vaccination after Vaccinia virus,25 the virus that causes cowpox. Because vaccination stimulates a long-lasting response by the body’s protective immune system, the term immunization is often used synonymously today. Jenner began the field of immunology—the study of the body’s defenses against pathogens. (Chapters 15–18 discuss immunology.) Pasteur later capitalized on Jenner’s work by producing weakened strains of various pathogens for use in preventing the serious diseases they cause. In honor of Jenner’s work with cowpox, Pasteur used the term vaccine to refer to all weakened, protective strains of pathogens. He subsequently developed successful vaccines against fowl cholera, anthrax, and rabies. Greek epi, meaning “upon”; demos, meaning “people”; and logos, meaning “word” or “study.” 24From Latin immunis, meaning “free.” 25From Latin vacca, meaning “cow.” 23From M01_BAUM7206_05_SE_C01.indd 17 Ehrlich’s “Magic Bullets” Gram’s discovery that stained bacteria could be differentiated into two types by color suggested to the German microbiologist Paul Ehrlich (1854–1915) that chemicals could be used to kill microorganisms differentially. To investigate this idea, Ehrlich undertook an exhaustive survey of chemicals to find a “magic bullet” that would destroy pathogens while remaining nontoxic to humans. By 1908, he had discovered a chemical active against the causative agent of syphilis, though the arsenic-based drug can have serious side effects in humans. His discoveries began the branch of medical microbiology known as chemotherapy. In summary, the Golden Age of Microbiology was a time when researchers proved that living things come from other living things, that microorganisms can cause fermentation and disease, and that certain procedures and chemicals can limit, prevent, and cure infectious diseases. These discoveries were made by scientists who applied the scientific method to biological investigation, and they led to an explosion of knowledge in a number of scientific disciplines (FIGURE 1.19). TELL ME WHY Some people consider Pasteur or Koch to be the Father of Microbiology, rather than Leeuwenhoek. Why might they be correct? The Modern Age of Microbiology LE A R N I N G O UTC O M E 1.19 List four major questions that drive microbiological investigations today. The vast increase in the number of microbiological investigations and in scientific knowledge during the 1800s opened new fields of science, including disciplines called environmental microbiology, immunology, epidemiology, chemotherapy, and genetic engineering (TABLE 1.3 on p. 19). Microorganisms played a significant role in the development of these disciplines because microorganisms are relatively easy to grow, take up little space, and are available by the trillions. Much of what has been learned about microbes also applies to other organisms, including humans. In the rest of this book we examine advances made in these branches of microbiology, though it would require thousands of books this size to deal with all that is known. Once the developing science of microbiology had successfully answered questions about spontaneous generation, fermentation, and disease, additional questions arose in each branch of the new science. In this section, we briefly consider some of the 20th century’s overarching questions in both basic and applied research. The chapter concludes with a look at some of the questions that might propel microbiological research for the next 50 years. 11/23/16 2:58 AM 1    A Brief H apter       Ch istory of Microbiology BIOLOGISTS MODERN DISCIPLINES Leeuwenhoek Bacteriology (bacteria) Protozoology (protozoa) Mycology (fungi) Parasitology (protozoa and animals) Phycology (algae) Linnaeus Taxonomy Semmelweis Snow Infection control Epidemiology Pre-1857 The Golden Age of Microbiology (1857–1907) Industrial microbiology Pasteur Pasteurization Microbial metabolism Genetics Genetic engineering Buchner Koch Food and beverage technology Koch’s postulates Etiology Ivanovsky Virology Beijerinck Winogradsky Environmental microbiology Ecological microbiology Gram Microbial morphology Lister Nightingale Antiseptic medical techniques Hospital microbiology Jenner von Behring Kitasato Serology Immunology Ehrlich Chemotherapy Fleming Pharmaceutical microbiology In contrast, microbiologists Albert Kluyver (1888–1956) and his student C. B. van Niel (1897–1985) proposed that basic biochemical reactions are shared by all living things, that these reactions are relatively few in number, and that their primary feature is the transfer of electrons and hydrogen ions. In adopting this view, scientists could use microbes as model systems to answer questions about metabolism in all organisms. Research during the 20th century validated this approach to understanding basic metabolic processes, but scientists have also documented an amazing metabolic diversity. (Chapter 5 discusses basic metabolic processes, and Chapter 6 considers metabolic diversity.) Basic biochemical research has many practical applications, including the following: • The design of herbicides and pesticides that are specific in their action and have no long-term adverse effects on the environment. • The diagnosis of illnesses and the monitoring of a patient’s responses to treatment. For example, physicians routinely monitor liver disease by measuring blood levels of certain enzymes and products of liver metabolism. • The treatment of metabolic diseases. One example is treating phenylketonuria, a disease resulting from the inability to properly metabolize the amino acid phenylalanine, by eliminating foods containing phenylalanine from the diet. • The design of drugs to treat leukemia, gout, bacterial infections, malaria, herpes, AIDS, asthma, and heart attacks. How Do Genes Work? Genetics, the scientific study of inheritance, started in the mid1800s as an offshoot of botany, but scientists studying microbes made most of the great advances in this discipline. Microbial Genetics ▲ FIGURE 1.19 Some of the many scientific disciplines and applications that arose from the pioneering work of scientists just before and around the time of the Golden Age of Microbiology. What Are the Basic Chemical Reactions of Life? Biochemistry is the study of metabolism—that is, the chemical reactions that occur in living organisms. Biochemistry began with Pasteur’s work on fermentation by yeast and bacteria and with Buchner’s discovery of enzymes in yeast extract, but by the early 1900s, many scientists thought that the metabolic reactions of microbes had little to do with the metabolism of plants and animals. M01_BAUM7206_05_SE_C01.indd 18 While working with the bacterium Streptococcus pneumoniae (strep-tō-kok′ŭs nū-mō′nē-ī), Oswald Avery (1877–1955), Colin MacLeod (1909–1972), and Maclyn McCarty (1911–2005) determined that genes are contained in molecules of DNA. In 1958, George Beadle (1903–1989) and Edward Tatum (1909–1975), working with the bread mold Neurospora crassa (noo-ros′pōr-ă kras′ă), established that a gene’s activity is related to the function of the specific protein coded by that gene. Other researchers, also working with microbes, determined the exact way in which genetic information is translated into a protein, the rates and mechanisms of genetic mutation, and the methods by which cells control genetic expression. (Chapter 7 examines all these aspects of microbial genetics.) Over the past 40 years, advances in microbial genetics developed into several new disciplines that are among the 11/23/16 2:58 AM       The Modern Age of Microbiology TABLE 1.3 Fields of Microbiology Disciplines Subject(s) of Study Basic Research Microbe Centered Bacteriology Bacteria and archaea Phycology Algae Mycology Fungi Protozoology Protozoa Parasitology Parasitic protozoa and parasitic animals Virology Viruses Process Centered Microbial metabolism Biochemistry: chemical reactions within cells Microbial genetics Functions of DNA and RNA Environmental microbiology Relationships between microbes and among microbes, other organisms, and their environment Applied Microbiology Medical Microbiology including humans and many of their pathogens. It is hoped that a fuller understanding of the genomes of organisms will result in practical ways to limit disease, repair genetic defects, and enhance agricultural yield. The American Nobel Prize winner Linus Pauling (1901– 1994) proposed in 1965 that gene sequences could provide a means of understanding evolutionary relationships and processes, establishing taxonomic categories that more closely reflect these relationships, and identifying the existence of microbes that have never been cultured in a laboratory. Two examples illustrate such uses of gene sequencing data: • In the 1970s, Carl Woese (1928–2012) and George Fox (1945–) discovered that significant differences in nucleic acid sequences among organisms clearly reveal that cells belong to one of three major groups—bacteria, archaea, or eukaryotes—and not merely two groups (prokaryotes and eukaryotes), as previously thought. • Scientists showed in 1990 that cat scratch disease is caused by a bacterium that had not been cultured. The bacterium was discovered by comparing the sequence of a portion of its ribonucleic acid with ribonucleic acid sequences from all other known bacteria. This is a standard technique in modern bacterial identification. Antibodies in blood serum, particularly as an indicator of infection Immunology Body’s defenses against specific diseases Epidemiology Frequency, distribution, and spread of disease Etiology Causes of disease Recombinant DNA Technology Infection control ygiene in health care settings and control of nosocomial infections Chemotherapy Development and use of drugs to treat infectious diseases Molecular biology is applied in recombinant DNA technology, 27 commonly called genetic engineering, which was first developed using microbial models. Geneticists manipulate genes in microbes, plants, and animals for practical applications. For instance, once scientists have inserted the gene for a human blood-clotting factor into the bacterium Escherichia coli (esh-ĕ-rik′ē-ă kō′lī), the bacterium produces the factor in a pure form. This technology is a benefit to hemophiliacs, who previously depended on clotting factor derived from donated blood, which was possibly contaminated by life-threatening viral pathogens. H Serology Bioremediation U Applied Environmental Microbiology se of microbes to remove pollutants Sewage treatment, water purification, and control of insects that spread disease Agricultural microbiology se of microbes to control insect pests U Public health microbiology Industrial Microbiology (Biotechnology) Food and beverage technology Reduction or elimination of harmful microbes in food and drink Pharmaceutical microbiology Manufacture of vaccines and antibiotics Recombinant DNA technology (genetic engineering) Alteration of microbial genes to synthesize useful products faster-growing areas of scientific research today, including molecular biology, recombinant DNA technology, and gene therapy. Molecular Biology Molecular biology combines aspects of biochemistry, cell biology, and genetics to explain cell function at the molecular level. Molecular biologists are particularly concerned with genome26 sequencing. Using techniques perfected on microorganisms, molecular biologists have sequenced the genomes of many organisms, M01_BAUM7206_05_SE_C01.indd 19 Gene Therapy An exciting new area of study is the use of recombinant DNA technology for gene therapy, a process that involves inserting a missing gene or repairing a defective one in human cells. In such procedures, researchers insert a desired gene into host cells, where it is incorporated into a chromosome and begins to function normally. Doctors have successfully treated several inherited immune deficiencies with gene therapy. (Chapter 8 examines recombinant DNA technology and gene therapy in more detail.) 26A genome is the total genetic information of an organism. 27Recombinant DNA is DNA composed of genes from more than one organism. 11/23/16 2:58 AM 1    A Brief H apter       Ch istory of Microbiology What Roles Do Microorganisms Play in the Environment? LE A R N I N G O U TC O M E S 1.20 Identify the field of microbiology that studies the role of microorganisms in the environment. 1.21 Name the fastest-growing scientific disciplines in micro- biology today. Ever since Koch and Pasteur, most research in microbiology has focused on pure cultures of individual species; however, microorganisms are not alone in the “real world.” Instead, they live in natural microbial communities in the soil, water, the human body, and other habitats, and these communities play critical roles in such processes as the production of vitamins and biore­ mediation—the use of living bacteria, fungi, and algae to detoxify polluted environments. Microbial communities also play an essential role in the decay of dead organisms and the recycling of chemicals such as carbon, nitrogen, and sulfur. Martinus Beijerinck discovered bacteria capable of converting nitrogen gas (N2) from the air into nitrate (NO3), the form of nitrogen used by plants, and the Russian microbiologist Sergei Winogradsky (1856–1953) elucidated the role of microorganisms in the recycling of sulfur. Together these two microbiologists developed laboratory techniques for several important aspects of environmental microbiology. Another role of microbes in the environment is the causation of disease. Although most microorganisms are not pathogenic, in this book (particularly in Chapters 18–24), we focus on pathogenic microbes because of the threat they pose to human health. We examine their characteristics and the diseases they cause as well as the steps we can take to limit their abundance and control their spread in the environment, such as sewage treatment, water purification, disinfection, pasteurization, and sterilization. How Do We Defend Against Disease? Why do some people get sick during the flu season while their close friends and family remain well? The germ theory of disease showed not only that microorganisms can cause diseases, but also that the body can defend itself—otherwise, everyone would be sick most of the time. The work of Jenner and Pasteur on vaccines showed that the body can protect itself from repeated diseases by the same organism. The German bacteriologist Emil von Behring (1854– 1917) and the Japanese microbiologist Shibasaburo Kitasato (1852–1931), working in Koch’s laboratory, reported the existence in the blood of chemicals and cells that fight infection. Their studies developed into the fields of serology, the study of blood U EMERGING DISEASE CASE ST DY Variant Creutzfeldt-Jakob Disease H Ellen screamed obscenities as she staggered from the room and collapsed in the hallway, jerking uncontrollably and unable to stand. er parents were shocked that their kind, considerate, and lovable daughter had changed so drastically during the past year. Sadly, she couldn’t even remember her siblings’ names. Ellen had joined the nearly 200 people afflicted with variant Creutzfeldt-Jakob disease (vCJD; what the media call “mad cow disease” because most humans with the condition acquired the pathogen from eating infected beef). Because vCJD affects the brain by slowly eroding nervous tissue and leaving the brain full of spongelike holes, the signs and symptoms of vCJD are neurological. Ellen’s disease started with insomnia, depression, and confusion, but eventually it led to uncontrollable emotional and verbal outbursts, inability to coordinate movements, coma, and death. Typically, the disease lasts about a year, and there is no treatment. Variant CJD resembles the rare genetic disorder CreutzfeldtJakob disease (named for its discoverers), which is caused by a mutation and occurs in the elderly. The difference is that the variant form of CJD results from an acquired infection and often strikes and kills college-aged people, like Ellen in our story. For more about vCJD, see pp. 621–623. 1. The vCJD pathogen is primarily transmitted when a person or animal consumes nervous tissue (brains). How could cattle become infected? 2. Why is vCJD called variant? 3. What effect does this pathogen have on cattle? 28Latin, M01_BAUM7206_05_SE_C01.indd 20 meaning “whey.” Serum is the liquid that remains after blood coagulates. 11/23/16 2:58 AM       The Modern Age of Microbiology Fungus colony (Penicillium) Zone of inhibition Bacteria (Staphylococcus) ▲ FIGURE 1.20 The effects of penicillin on a bacterial “lawn” in a Petri dish. The clear area (zone of inhibition) surrounding the fungus colony, which is producing the antibiotic, is where the penicillin prevented bacterial growth. serum 28—specifically, the chemicals in the liquid portion of blood that fight disease—and immunology, the study of the body’s defense against specific pathogens. (Chapters 15–18 cover these aspects of microbiology, which are of utmost importance to physicians, nurses, and other health care practitioners.) Ehrlich introduced the idea of a “magic bullet” that would kill pathogens, but it was not until Alexander Fleming (1881– 1955) discovered penicillin (FIGURE 1.20) in 1929 and Gerhard Domagk (1895–1964) discovered sulfa drugs in 1935 that medical personnel finally had drugs effective against a wide range of bacteria. (We study chemotherapy and some physical and chemical agents used to control microorganisms in the environment in Chapters 9 and 10.) Health care workers are concerned about emerging diseases—ones that have been diagnosed in a population for the first time or are rapidly increasing in incidence or geographic range. Notable examples include Middle East respiratory syndrome (MERS), Zika fever, chikungunya, and Ebola hemorrhagic fever. The Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, have called these diseases “the new normal” in health care. Further, diseases once thought to be near eradication, such as measles, whooping cough, and tuberculosis, have reemerged in troubling outbreaks. Other near-vanquished pathogens such as smallpox or anthrax could become potential weapons in bioterrorist attacks. How do emerging and reemerging diseases arise? Some are introduced to humans as we move into remote jungles and contact infected animals, some are carried by insects whose range is spreading, and some previously harmless microbes acquire new genes that allow them to be infective and cause disease. Some emerging and remerging pathogens spread with M01_BAUM7206_05_SE_C01.indd 21 the speed of jet planes carrying infected people around the globe, and still others arise when previously treatable microbes develop resistance to our antibiotics. Throughout this text, you will encounter many boxed discussions of such emerging and reemerging diseases. What Will the Future Hold? Science is built on asking and answering questions. What began with the questioning curiosity of a dedicated lens grinder in the Netherlands has come far in the past 350 years, expanding into disciplines as diverse as immunology, recombinant DNA technology, and bioremediation. However, the adage remains true: The more questions we answer, the more ques­ tions we have. What will microbiologists discover next? Among the questions for the next 50 years are the following: • How can we develop successful programs to control or eradicate diseases such as tuberculosis, malaria, AIDS, and Ebola? • What is it about the physiology of life forms known only by their nucleic acid sequences that has prevented researchers from growing them in the laboratory? • Can bacteria and archaea be used in ultraminiature technologies, such as living computer circuit boards? • How can an understanding of microbial biofilms— aggregates of microbial cells growing together on a surface—help us understand aspects of microbial action in preventing and curing diseases, recycling nutrients, degrading pollutants, and moderating climate change? • How can we reduce the threat from microbes resistant to antimicrobial drugs, particularly so-called persistent cells that resist antimicrobial treatment without acquiring genetic changes? • Can we develop inexpensive, rapid, accurate, and simple tests for infections? • Can microorganisms that grow normally in the body bolster our ability to fight disease, lose weight, and maintain good mental health? • Can microorganisms or their genes be used to develop sustainable fuels or bioremediate synthetic chemicals? TELL ME WHY Why are so many modern questions in microbiology related to genetics? 11/23/16 2:58 AM istory of Microbiology Too Much Cake, or Something Worse? H Dr. Andrews has a lot of questions for Patty. When did she start feeling poorly? When did the diarrhea start? ow long after the diarrhea started did she start vomiting? Patty feels terrible and is somewhat annoyed with the doctor—she already told the nurse most of this information, so why does he need to ask again? Dr. Andrews tells Patty that he suspects Patty may have food poisoning, and for public health reasons it’s necessary to try to track down the source. Dr. Andrews gets a complete list of the foods that Patty consumed over the last 48 hours, including where they were consumed. The doctor collects a stool (feces) sample from Patty and sends it to the lab for analysis. The results come back positive for norovirus. Dr. Andrews asks Patty whether anyone else at her weekend events has gotten sick or whether anyone at the parties had been sick in the not-too-distant past. Patty said that some of the other people at the barbecue who had eaten meat were feeling poorly; she M01_BAUM7206_05_SE_C01.indd 22 thought that since she ate only fruit salad at the barbecue, she couldn’t have the same thing they had. She also knew that the family that hosted the barbecue had a child home sick from daycare the week before. Dr. Andrews tells Patty that it’s likely that the fruit salad became contaminated with noroviruses and that this is where Patty got the infection. Since norovirus is viral, typical antibacterial drugs such as penicillin cannot be used as treatment. Dr. Andrews tells Patty to rest as much as she can and drink a lot of water to prevent dehydration; she should start feeling better in a day or two. 1. How does Patty’s diagnostic conversation with Dr. Andrews parallel the scientific method? 2. Based on what you know about Patty’s case, can you form a hypothesis about how the fruit salad became contaminated? Check your answers to Micro in the Clinic Follow- p questions in the MasteringMicrobiology Study Area. U 1    A Brief H apter       Ch 11/23/16 2:58 AM       Questions for Review CHAPTER SUMMARY The Early Years of Microbiology (pp. 2–7) 1. Leeuwenhoek’s observations of microbes introduced most types of microorganisms to the world. His discoveries were named and classified by Linnaeus in his taxonomic system. 2. Small prokaryotes—bacteria and archaea—live in a variety of communities and in most habitats. Even though some cause disease, most are beneficial. 3. Relatively large microscopic eukaryotic fungi include molds and yeasts. 4. Animal-like protozoa are single-celled eukaryotes. Some cause disease. 5. Plantlike eukaryotic algae are important providers of oxygen, serve as food for many marine animals, and make chemicals used in microbiological growth media. 6. Parasitic worms, the largest organisms studied by microbiologists, are often visible without a microscope, although their immature stages are microscopic. 7. Viruses, the smallest microbes, are so small they can be seen only with an electron microscope. The Golden Age of Microbiology (pp. 7–17) 5. The procedure for the Gram stain was developed in the 1880s and is still used to differentiate bacteria into two categories: Gram positive and Gram negative. 6. The investigations of Semmelweis, Lister, Nightingale, and Snow are the foundations on which infection control, including control of healthcare-associated infections (HAI), or nosocomial infections, and epidemiology are built. 7. Jenner’s use of a cowpox-based vaccine for preventing smallpox began the field of immunology. Pasteur significantly advanced the field. 8. Ehrlich’s search for “magic bullets”—chemicals that differentially kill microorganisms—laid the foundations for the field of chemotherapy. The Modern Age of Microbiology (pp. 17–21) 1. Microbiology in the modern age has focused on answering questions regarding biochemistry, which is the study of metabolism; microbial genetics, which is the study of inheritance in microorganisms; and molecular biology, which involves investigations of cell function at the molecular level. 2. Scientists have applied knowledge from basic research to answer questions in recombinant DNA technology and gene therapy. ideo V Tu tor 1. The study of the Golden Age of Microbiology includes a look at the men who proposed or refuted the theory of spontaneous generation: Aristotle, Redi, Needham, Spallanzani, and Pasteur (the Father of Microbiology). The scientific method that emerged then remains the accepted sequence of study today. 4. Koch initiated careful microbiological laboratory techniques in his search for disease agents. Koch’s postulates, the logical steps he followed to prove the cause of an infectious disease, remain an important part of microbiology today. 2. The study of fermentation by Pasteur and Buchner led to the discovery of anaerobic bacteria, to the fields of industrial microbiology (biotechnology) and biochemistry, and to the study of metabolism. 3. Koch, Pasteur, and others proved that pathogens cause infectious diseases, an idea that is known as the germ theory of disease. Etiology is the study of the causation of diseases. 3. The study of microorganisms in their natural environment is environmental microbiology. 4. The discovery of chemicals in the blood that are active against specific pathogens advanced immunology and began the field of serology. 5. Advancements in chemotherapy were made in the 1900s with the discovery of numerous substances, such as penicillin and sulfa drugs, that inhibit pathogens. U Q ESTIONS FOR REVIEW Answers to the Questions for Review (except Short Answer questions) begin on p. A-1. Multiple Choice 1. Which of the following microorganisms are not eukaryotic? a. bacteria c. molds b. yeasts d. protozoa 3. In which habitat would you most likely find archaea? a. acidic hot springs c. Great Salt Lake b. swamp mud d. all of the above 2. Which microorganisms are used to make microbiological growth media? a. bacteria c. algae b. fungi d. protozoa 4. Of the following scientists, who first promulgated the theory of abiogenesis? a. Aristotle c. Needham b. Pasteur d. Spallanzani M01_BAUM7206_05_SE_C01.indd 23 11/23/16 2:58 AM istory of Microbiology b. Louis Pasteur d. Richard Petri 6. Which scientist first hypothesized that medical personnel can infect patients with pathogens? a. Edward Jenner c. John Snow b. Joseph Lister d. Ignaz Semmelweis 7. Leeuwenhoek described microorganisms as __________________. a. animalcules c. eukaryotes b. prokaryotes d. protozoa 8. Which of the following favored the theory of spontaneous generation? a. Spallanzani c. Pasteur b. Needham d. Koch 9. A scientist who studies the role of microorganisms in the environment is a(n) __________________. a. genetic technologist c. epidemiologist b. earth microbiologist d. environmental microbiologist 10. The laboratory of Robert Koch contributed which of the following to the field of microbiology? a. simple staining technique b. use of Petri dishes c. first photomicrograph of bacteria d. all of the above Fill in the Blanks Fill in the blanks with the name(s) of the scientist(s) whose investigations led to the following fields of study in microbiology. 1. Environmental microbiology __________________ and __________________ 2. Biochemistry __________________ and __________________ 3. Chemotherapy __________________ 4. Immunology __________________ 5. Infection control __________________ 6. Etiology __________________ 7. Epidemiology __________________ 8. Biotechnology __________________ 9. Food microbiology __________________ M01_BAUM7206_05_SE_C01.indd 24 1. Why was the theory of spontaneous generation a hindrance to the development of the field of microbiology? 2. Discuss the significant difference between the flasks used by Pasteur and Spallanzani. How did Pasteur’s investigation settle the dispute about spontaneous generation? 3. List six types of microorganisms. 4. Defend this statement: “The investigations of Antoni van Leeuwenhoek changed the world forever.” 5. Why would a macroscopic tapeworm be studied in microbiology? 6. Describe what has been called the “Golden Age of Microbiology” with reference to four major questions that propelled scientists during that period. 7. List four major questions that drive microbiological investigations today. 8. Refer to the four steps in the scientific method in describing Pasteur’s fermentation experiments. 9. List Koch’s postulates, and explain why they are significant. 10. What does the term HAI (nosocomial infection) have to do with patient care? Matching Match each of the following descriptions with the person it best describes. An answer may be used more than once. 1. _____ Developed smallpox immunization  c. Robert Koch 2. _____ First photomicrograph of bacteria  a. Antoni van Leeuwenhoek Short Answer 3. _____ Germ theory of disease 4. _____ Germs cause disease 5. _____ Sought a “magic bullet” to destroy pathogens  5. Which of the following scientists hypothesized that a bacterial colony arises from a single bacterial cell? A. John Snow B. Paul Ehrlich C. Louis Pasteur D. Antoni van Leeuwenhoek E. Carolus Linnaeus F. John Needham 6. _____ Early epidemiologist G. Eduard Buchner 7. _____ Father of Microbiology H. Robert Koch 8. _____ Classification system 9. _____ Discoverer of bacteria I. Joseph Lister 10. _____ Discoverer of protozoa 11. _____ Founder of antiseptic surgery 12. _____ Developed the most widely used bacterial staining technique J. Edward Jenner K. Girolamo Fracastoro  H       Chapter 1   A Brief L. Hans Christian Gram 06/03/2018 10:50       Questions for Review VISUALIZE IT! 1. On the photos below, label cilium, flagellum, nucleus, and pseudopod. 1 2 3 2. Show where microbes ended up in Pasteur’s experiment. 4 H CRITICAL T INKING 1. If Robert Koch had become interested in a viral disease, such as influenza, instead of anthrax (caused by a bacterium), how might his list of lifetime accomplishments be different? Why? 7. Compare and contrast the investigations of Redi, Needham, Spallanzani, and Pasteur in relation to the idea of spontaneous generation. 2. In 1911, the Polish scientist Casimir Funk proposed that a limited diet of polished white rice (rice without the husks) caused beriberi, a disease of the central nervous system. Even though history has proven him correct—beriberi is caused by a thiamine deficiency, which in his day resulted from unsophisticated milling techniques that removed the thiamine-rich husks—Funk was criticized by his contemporaries, who told him to find the microbe that caused beriberi. Explain how the prevailing scientific philosophy of the day shaped the point of view of Funk’s detractors. 8. If you were a career counselor directing a student in the field of applied microbiology, describe three possible disciplines you could suggest. 3. Haemophilus influenzae does not cause flu, but it received its name because it was once thought to be the cause. Explain how a proper application of Koch’s postulates would have prevented this error in nomenclature. 4. Just before winter break in early December, your roommate stocks the refrigerator with a gallon of milk, but both of you leave before opening it. When you return in January, the milk has soured. Your roommate is annoyed because the milk was pasteurized and thus should not have spoiled. Explain why your roommate’s position is unreasonable. 9. A few bacteria produce disease because they derive nutrition from human cells and produce toxic wastes. Algae do not typically cause disease. Why not? 10. How might the debate over spontaneous generation have been different if Buchner had conducted his experiments in 1857 instead of 1897? 11. French microbiologists, led by Pasteur, tried to isolate a single bacterium by diluting liquid media until only a single type of bacterium could be microscopically observed in a sample of the diluted medium. What advantages does Koch’s method have over the French method? 12. Why aren’t Koch’s postulates always useful in proving the cause of a given disease? Consider a variety of diseases, such as cholera, pneumonia, Alzheimer’s, AIDS, Down syndrome, and lung cancer. 5. Design an experiment to prove that microbes do not spontaneously generate in milk. 13. Albert Kluyver said, “From elephant to . . . bacterium—it is all the same!” What did he mean? 6. The British General Board of Health concluded in 1855 that the Broad Street cholera epidemic discussed in the chapter (see p. 17) resulted from fermentation of “nocturnal clouds of vapor” from the polluted Thames River. How could an epidemiologist prove or disprove this claim? 14. The ability of farmers around the world to produce crops such as corn, wheat, and rice is often limited by the lack of nitrogen-based fertilizer. How might scientists use Beijerinck’s discovery to increase world supplies of grain? M01_BAUM7206_05_SE_C01.indd 25 11/23/16 2:58 AM M H istory of Microbiology ING APP CONC EPT       Chapter 1   A Brief Using the following terms, fill in the following concept map that describes what microbiologists study. Obligate intracellular parasites Protozoa Unicellular Yeasts Bacteria Eukaryotes Molds Multicellular Acellular Algae Animal-like Archaea Microbiologists study 1 Prokaryotes such as such as 4 Fungi including 6 which are 2 3 which are which are Parasitic worms which are which are 8 which are Unicellular Viruses which are 11 12 7 5 Animal-like 10 9 or Multicellular Multicellular M01_BAUM7206_05_SE_C01.indd 26 Unicellular Photosynthetic 06/03/2018 10:53