Microbiology Chapter 1 Answers

Image: Label the figures to identify the locomotive structures in protozoa. Drag the appropriate labels to their respective targets. What was Leeuwenhoek's contribution to the science of microbiology? He was the first to observe live microorganisms through a microscope. How are the bacteria and the archaea different from all the other cellular microbes? They have no nucleus. A microorganism has the following characteristics: eukaryotic, multicellular, has cell walls, and grows in long filaments. What is its general classification? fungus You have isolated microorganisms that are green, photosynthetic, have a cell wall, and do NOT possess a nucleus. These organisms are __________. bacteria Which of the following is NOT an example of a fungus? algae Which of the following is a true statement concerning bacteria and archaea? While some bacteria are pathogenic to humans, no archaea are known to cause human diseases. All of the following individuals showed that cleanliness played a role in human disease EXCEPT __________. Jenner Koch's work involving anthrax was significant because it was the first time __________. bacterium had been proven to cause a disease Whose experiments supported the existence of a "life force"? Needham Put the following steps of Koch's postulates in order: a. The suspected infectious agent must be isolated and grown outside the host. (2) b. The suspected infectious agent causes the disease when it is introduced to a healthy, experimental host.(3) c.The suspected infectious agent must be found in every case of the disease. (1) d. The suspected infectious agent must be found in the diseased experimental host.(4) C] c, a, b, d Remedy for Fever or Prescription for Death? In the late 18th century, Philadelphia was one of the larger and wealthier cities in the United States and served as the capital. That changed in 1793. The city had an unusually wet spring, which left behind swamps and stagnant pools that became breeding grounds for mosquitoes. Later, refugees from the slave revolution in Haiti 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 forced another 30% to flee for their lives. Victims suffered from high fever, nausea, skin eruptions, black vomit, and jaundice. The treatment, however, was 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 bloodletÝng would stem fever. These attempted remedies were more harmful than helpful, leaving the patients tired, weak, and unable to fight the infection. Without effective treatments, the epidemic stopped only when the first frost arrived. 1. What is the vector for transmission of yellow fever? Aedes aegypti mosquitoes 2. Why is this disease called “yellow fever”? Patients have yellow mucous membranes and an elevated temperature. 3. Yellow fever is caused by a(n) _____. virus 4.What is the best way to prevent the spread of yellow fever? Drain standing water and sleep under mosquito netÝng. 5. Who is credited with the discovery of the cause of yellow fever? Walter Reed Which of the following is NOT a growing area of microbial study? methods of disease transmission Which field of microbiology involves the study of microorganisms in their natural habitats? environmental microbiology Which of the following techniques could be used to produce a yeast capable of making viral proteins? recombinant DNA technology Which of the following fields of modern microbiology is NOT directly concerned with the genetic characteristics of a cell? bioremediation George is a healthy 28-year-old man. He enjoys an active lifestyle, including playing on an intramural Ultimate Frisbee team. Last weekend, while at a meet, George got a cut on his leg, just above the knee. It wasn’t very deep, and he cleaned the wound thoroughly when he got home. A few days later, the cut didn’t seem to be healing as George would have expected. It was a little sore, and he was worried that it might have been infected, so he decided to go his local outpatient clinic to have it examined. At the clinic, Dr. Smith examines the wound. He tells George that it looks like it might be infected, so he prescribes a broad-spectrum antibiotic, tells George to keep the wound clean, and sends him home. Over the next week, George becomes concerned when the wound doesn’t get any better—in fact, it starts to get worse. The affected area has become larger, and it is sorer than it was earlier. George makes a second appointment to see Dr. Smith. On the second visit, Dr. Smith takes a swab from the wound area for culturing. He instructs George to continue the oral antibiotics and also prescribes an antibiotic wash to use on the affected area. A couple of days later, the lab results come back and indicate that George’s wound is infected with Staphylococcus aureus. This colorized scanning electron micrograph of S. aureus illustrates how the scientific name of an organism can provide clues about the organism. For example, Staphylo- indicates the clustered arrangement of the cells, and -coccus indicates that the organisms are spherical in shape. Although you can’t tell from the micrograph, the aureus part of the name is derived from the fact that the colonies look yellow (aureus = golden) when grown on solid media. 1. Staphylococcus aureus (remember that an organism’s scientific name can also be written with the genus name abbreviated—in this case, S. aureus) is a bacterium, one of the groups of microorganisms. Although the different groups of microorganisms share some similarities, there are several important differences that distinguish each group. Drag each of the following statements to the appropriate bin to indicate whether it is a characteristic of bacteria, archaea, fungi, or viruses. 2. One of the first set of experiments to refute spontaneous generation was done in 1688 by Francesco Redi. Which of the following statements regarding Francesco Redi's experiments is true? The results of his experiment demonstrated that living organisms are derived from other living organisms. 3. In 1861, Pasteur conducted his now-famous experiments using flasks with long necks bent into an S-shape. Imagine that you are a scientist working in Pasteur's lab at this time. You decide to tip the flasks so that broth enters the long S-shaped neck. You then return the flask to its upright position. Predict the most likely outcome of tipping one of Pasteur's S-necked flasks. The broth would become contaminated with microbes because they were trapped in the neck. 4. S. aureus has been isolated from George’s infected wound. To satisfy Koch’s postulates, what would George’s doctor need to do with the isolated S. aureus? Inject the S. aureus into an animal, observe whether the animal gets an infection similar to George’s, and isolate the same strain of S. aureus from the infection. Which of the following are limitations of antibiotics? Select all that apply. A. Antibiotics are not effective in treating viral infections. C. Treatment with antibiotics can lead to the emergence of resistant strains. D. Antibiotics may be toxic. Further characterization of the S. aureus isolated from George’s wound reveals that the strain is MRSA. Why is George’s doctor concerned that MRSA has been identified as the causative agent of George’s infection? MRSA is transmissible. Which of the following would contain teichoic acids? a Gram-positive cell wall Which of the following is NOT a basic process of life? sexual reproduction Which of the following is NOT a characteristic of a eukaryotic cell? can undergo transcription and translation simultaneously Which of the following statements about bacterial flagella is true? Flagella can rotate 360 degrees. Taxis is A movement towards or away from a stimulus. Which of the following terms refers to a bacterium moving towards a light source? Positive phototaxis As a bacterium approaches a food source, one would expect runs to become more frequent. Why are receptors on the cell surface necessary for bacterial movement? The receptors sense the stimulus and send signals to the flagella. Which of the following scenarios is an example of bacterial motility? A bacterium moving towards a food source Axial filaments are found on spirochetes. A bacterial cell possesses a glycocalyx. Which of the following is FALSE? It will be engulfed more quickly by defensive cells of the host. Peptidoglycans are composed of sugars and _____. amino acids One chain of alternating NAGs and NAMs is connected to another chain via _____. tetrapeptides One of the main differences between a Gram-positive and a Gram-negative bacterial cell wall is that the peptidoglycan portion of a Gram-positive cell wall is _____ as compared to a Gramnegative cell wall. thicker Within the peptidoglycan layer, the crossbridges that connect the chains of alternating sugar molecules extend between _____. two N-acetylmuramic acid molecules The peptidoglycan cell wall of bacteria is most analogous to _____. a chain-link fence What role do the teichoic acids play within the cell wall of Gram-positive bacteria? They serve to stabilize the cell wall and hold it in place. The region between the outer and inner membranes of a Gram-negative bacterial cell is known as the __________, and it is the location of enzymes that assemble peptidoglycan. periplasmic space A patient is infected with Gram-negative bacteria and is experiencing only mild symptoms. When the patient is given an antibiotic causing lysis of the bacterial cells, he suddenly experiences an increase in inflammation and fever, as well as the formation of blood clots. What explanation best describes what happened? The lysis of the cells releases lipid A from the lipopolysaccharide layer. Which of the following molecules would be blocked by a cell membrane? IONS Hydrophobic molecules move across a membrane by passive transport directly across the membrane. What is a hallmark of passive transport across cell membranes? It occurs along an electrochemical gradient, and may involve the use of transport proteins. A positively charged sodium ion would require the use of integral protein channels to pass through a cell membrane. Which of the following statements regarding active transport is false? It powers the diffusion of water across the cell membrane. Which of the following would NOT be found in the cytoplasm of a bacterial cell? porins Which of the following would NOT be expected to be present in a biochemical analysis of an archaeal cell? peptidoglycan In a hypotonic environment, the volume of a plant cell enlarges as the cytoplasm pushes against the cell wall. Which organelles are most likely able to store that extra water? vacuoles How are the bacteria and the archaea different from all the other cellular microbes? They have no nucleus. Microbiologists study parasitic worms because __________. they cause diseases that are diagnosed by finding microscopic eggs in clinical specimens Spallanzani's experiments concerning spontaneous generation were NOT universally accepted because __________. he eliminated air from his flasks by sealing them Which of the following techniques could be used to produce a yeast capable of making viral proteins? recombinant DNA technology Which of the following refers to the use of bacteria or other microbes to detoxify pollutants? bioremediation Which of the following is a trait shared by both archaea and protozoa? They are unicellular. What characteristic is shared by both molds and parasitic worms? They are multicellular. They are studied by microbiologists. They are eukaryotic. All of the above are true. Viruses are unlike other infectious agents studied by microbiologists in that they are _______________. acellular What is the vector for transmission of yellow fever? Aedes aegypti mosquitoes Why is this disease called "yellow fever"? Patients have yellow mucous membranes and an elevated temperature. Jaundice results from liver damage and is observed as yellow discoloration of mucous membranes. Patients also have a fever. Yellow fever is caused by a(n) _____. virus Yellow fever is caused by a flavivirus. What is the best way to prevent the spread of yellow fever? Drain standing water and sleep under mosquito netÝng. Who is credited with the discovery of the cause of yellow fever? Walter Reed Walter Reed and his team of physicians showed that yellow fever was caused by a filterable agent (virus) and transmitted by a mosquito vector. Put the steps of the scientific method in the order that should be followed to identify the virus causing a disease: 1. Observe a natural phenomenon or reaction 2. Devise an explanation of what you have observed 3. Experiment to support or refute your explanation 4. Record the results of your experiments 5. Determine whether your results support or refute your explanation 6. Decide whether you need to rewrite your explanation or it has withstood testing The scientific method is series of steps to follow that will allow you to examine something in nature and develop a means to explain what you have observed. By observing, developing a hypothesis, and conducting experiments based on your hypothesis, the analysis of the results will allow you to determine whether your hypothesis is viable or should be modified to explain your observations. The tests for these uncommon pathogens are similar to the ones that have already been performed for the common viruses, but in this case, you will try to identify the DNA or proteins of specific viruses that are not often seen in clinics or hospitals in that area of the country. Each region of the country has certain viral pathogens that are spread throughout the human population that live in that area. When one of these viruses spreads to a new area, we consider it to be "emerging" in this new population of people. Some detective work and deductions will be required. By applying the scientific method, you can focus and refine your list of possible viral pathogens to experimentally test for. You'll begin your investigation by reviewing the patient's history and symptoms and formulating a hypothesis for possible causative agents. Based on what you know of the scientific method, what would you like to do next? Choose what your next step should be. Design and run some tests or experiments. Record your test results. Review the patient's charts again. Revise your list of possible viruses. Design and run some tests or experiments. You have successfully completed the experiments and analyzed your results. Your analysis has allowed you to refine you hypothesis and remove all but one virus strain from your list of possible causative agents. With your success at identifying the viral pathogen, you will now need to begin the long process of characterization, the studying of all aspects of an organism to determine whether this virus is truly new or has been isolated and identified before. The characterization will begin with studying the genome of this pathogen. Sequencing machines will determine the order of the nucleic acids that make up the viral genome, and computers will be able to analyze this sequence to determine the genes available for this virus. What is the area of biology that studies the nucleic acid makeup of an organism? Pick the area of biology that studies DNA and chromosomes. genetics Although sequencing the DNA of a virus can help you identify and characterize its properties, you still need to ensure that the virus you have isolated is actually the pathogenic organism that has caused the disease. If you have other patients with the same symptoms and the same virus, you may be able to find a causal link. However, since your virus is rarely seen in the clinics, it may take a long time for you to gather enough suitable samples to make your case. Fortunately, with animal testing and computer modeling you have means of proving that this virus is the cause of the disease. In the late 1800s, a researcher by the name of Robert Koch developed a series of postulates (guidelines) that can be used to prove that a given pathogen is the true cause of a disease. Koch's Postulates 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 must get the disease. 4. The same agent must be found in the diseased experimental host. Which of the following steps does NOT follow one of Koch's postulates? Pick step that does NOT follow the postulates. You are able to isolate a pathogenic bacterium from someone with a new type of pharyngitis. You collect a throat swab from a family member who has also become sick. A mouse that was exposed to a potential viral pathogen has died and you are able to isolate the virus from the liver of the mouse. You give a patient an antibiotic to treat an infection. You give a patient an antibiotic to treat an infection. Drag each of the following statements to the appropriate bin to indicate whether it is a characteristic of bacteria, archaea, fungi, or viruses. Bacteria: have cell walls that contain peptidoglycan, derive nutrition from organic or inorganic sources or conduct photosynthesis. Archae: found in extreme environments, not typically associated with human disease. Fungi: eukaryotic, can be unicellular or multicellular Viruses: can be seen only with an electron microscope, cannot survive outside a host cell. The unique characteristics of each group of microorganisms not only are used to classify them, but also have implications for the relationship between humans and microbes. For example, the metabolic characteristics of microbes make them commercially useful in processes such as fermentation and bioremediation. Furthermore, structural characteristics of microbes are often targeted during the treatment of human disease. One of the first set of experiments to refute spontaneous generation was done in 1688 by Francesco Redi. Which of the following statements regarding Francesco Redi's experiments is true? The results of his experiment demonstrated that living organisms are derived from other living organisms. Redi's work set the stage for subsequent experiments testing spontaneous generation. In 1858, Rudolf Virchow put forth the concept of biogenesis: that living cells can arise only from other living cells. Work done by Louis Pasteur provided key evidence in support of Virchow's idea of biogenesis. In 1861, Pasteur conducted his now-famous experiments using flasks with long necks bent into an S-shape. Imagine that you are a scientist working in Pasteur's lab at this time. You decide to tip the flasks so that broth enters the long S-shaped neck. You then return the flask to its upright position. Predict the most likely outcome of tipping one of Pasteur's S-necked flasks. The broth would become contaminated with microbes because they were trapped in the neck. The boiling of the broth eliminated any microbes that were present. Although microbes from the air were able to enter the long neck, the S shape prevented them from entering the flask. Even after long periods of time, the broth remained free of microbes. In fact, one of Pasteur's flasks remains uncontaminated and is on display at the Pasteur Institute. S. aureus has been isolated from George's infected wound. To satisfy Koch's postulates, what would George's doctor need to do with the isolated S. aureus? Inject the S. aureus into an animal, observe whether the animal gets an infection similar to George's, and isolate the same strain of S. aureus from the infection. The work of Robert Koch was the first definitive evidence of a link between microbes and disease. To satisfy the postulates, the organism must be isolated and cultured from the patient. The organism will then be used to infect an animal, and the animal will then be observed for development of the same infection. The organism must then be isolated from the animal and identified as the same organism isolated from the original patient. Which of the following are limitations of antibiotics? Select all that apply. Antibiotics are not effective in treating viral infections. Treatment with antibiotics can lead to the emergence of resistant strains. Antibiotics may be toxic. The problem of antibiotic resistance is now described as a global health crisis. S. aureus is a perfect example of how quickly resistance can emerge and become a significant health issue. Penicillin was first used to treat infections in 1941; by 1942, resistant strains were identified. In 1960, methicillin was introduced to the market; by 1961, resistant strains of S. aureus had been isolated (MRSA). In 1997, partial (intermediate) vancomycin resistance was identified in S. aureus. In 2002, full resistance to vancomycin was reported in S. aureus. Further characterization of the S. aureus isolated from George's wound reveals that the strain is MRSA. Why is George's doctor concerned that MRSA has been identified as the causative agent of George's infection? MRSA is transmissible. Although there are effective treatment approaches for MRSA, Dr. Smith's concern is warranted. MRSA is transmissible between people; an outbreak can occur when an infected person comes in contact with others in a health care or community setÝng. In fact, it is possible that George acquired the infection at the outpatient clinic. Simple practices, such as good handwashing techniques and screening patients and workers for MRSA, can help decrease the spread of MRSA. What is spontaneous generation? the theory that living organisms may arise from nonliving matter Yes. The theory of spontaneous generation was developed to explain how life seems to come from nonliving matter. An example would be the production of maggots from decaying meat. How did Francesco Redi attempt to disprove the theory of spontaneous generation? He boiled vials of beef gravy and infusions of plant material for almost an hour and bent the necks of the vials into an S-shape, allowing the entrance of air. He boiled vials of beef gravy and infusions of plant material, and then tightly sealed them with a cork. He boiled vials of beef gravy and infusions of plant material for almost an hour and then tightly sealed them by melting the necks of the vials. He performed a series of experiments involving decaying meat and maggots. He performed a series of experiments involving decaying meat and maggots. Yes. Redi showed that maggots do not spontaneously arise from nonliving meat, but instead come from flies depositing eggs. Which scientist definitively ended the debate over spontaneous generation? Louis Pasteur Francesco Redi John T. Needham Lazzaro Spallanzani Louis Pasteur Yes. Through the use of vials with S-shaped necks, Pasteur was finally able to disprove the theory of spontaneous generation. Which of the following steps is NOT included in the scientific method? Repeat experiment until desired result is achieved. Yes. If an experiment yields results contradictory to the hypothesis, it is then necessary to reject or modify the hypothesis rather than repeat the experiment. When conducting an experiment, it is generally necessary to include __________ groups that are treated exactly the same as treatment groups except for the condition being tested. control Yes. Typically, control groups serve to eliminate all other conditions in an experiment, besides the ones being tested. If the results from an experiment contradict the hypothesis, what should be a scientist's next step? The scientist should reject or modify the hypothesis. Yes. If the results of the experiment do not align with the hypothesis, it is necessary to either reject the hypothesis or change the hypothesis and retest it. Some critics of Spallanzani's experiments thought that the reason sealed flasks were unable to spontaneously generate microorganisms was that there was not enough air present to support life. How did Louis Pasteur respond to this claim? He modified the experiment to include air as treatment. Yes. When an experiment does not take into account all variables, it may be necessary to include more treatments within the experiment. What is a hypothesis? A hypothesis is a possible answer to a scientific question. Yes. A hypothesis is an informed explanation for an observed phenomenon. Which of the following observations would suggest that a plate was inoculated with a pure (axenic) culture? Isolated colonies are all white in color and about the same size. Imagine that you forgot to flame the loop before streaking the inoculum from the first quadrant into the second quadrant. What is the most likely consequence of this error? Too much bacterial growth outside the first quadrant. Proper streak plating technique deposits progressively smaller amounts of bacteria in each quadrant. This is done by having the loop pick up only a small amount of bacteria from the previous quadrant's streaks. Flaming the loop between streaks ensures that the loop starts clean and that only this small amount of bacteria is used to inoculate the next quadrant.