Characteristics and Roles of Bacteria

Bacteria are found in nearly every habitat on earth, including within and on humans. Most bacteria are harmless or helpful, but some are pathogens, causing disease in humans and other animals. Bacteria are prokaryotic because their genetic material (DNA) is not housed within a true nucleus. Most bacteria have cell walls that contain peptidoglycan. Archaea are also unicellular prokaryotic organisms. Archaea and bacteria have different evolutionary histories, as well as significant differences in genetics, metabolic pathways, and the composition of their cell walls and membranes. Unlike most bacteria, archaeal cell walls do not contain peptidoglycan, but their cell walls are often composed of a similar substance called pseudopeptidoglycan. Like bacteria, archaea are found in nearly every habitat on earth, even extreme environments that are very cold, very hot, very basic, or very acidic. Some archaea live in the human body, but none have been shown to be human pathogens. Protists are an informal grouping of eukaryotes that are not plants, animals, or fungi. Protozoa are protists that make up the backbone of many food webs by providing nutrients for other organisms. Protozoa are very diverse. Some protozoa move with help from hair-like structures called cilia or whip-like structures called flagella. Others extend part of their cell membrane and cytoplasm to propel themselves forward. These cytoplasmic extensions are called pseudopods (“false feet”). Some protozoa are photosynthetic; others feed on organic material. Some are free-living, whereas others are parasitic, only able to survive by extracting nutrients from a host organism. Most protozoa are harmless, but some are pathogens that can cause disease in animals or humans Algae are mostly made up of protists that can be either unicellular or multicellular and vary widely in size, appearance, and habitat. Algal protists are surrounded by cell walls made of cellulose, a type of carbohydrate. Fungi (singular: fungus) are also eukaryotes. Some multicellular fungi, such as mushrooms, resemble plants, but they are actually quite different. Fungi are not photosynthetic, and their cell walls are usually made out of chitin rather than cellulose. Some yeasts have beneficial uses, such as causing bread to rise and beverages to ferment; but yeasts can also cause food to spoil. Some even cause diseases, such as vaginal yeast infections and oral thrush. Multicellular parasitic worms called helminths are not technically microorganisms, as most are large enough to see without a microscope. However, these worms fall within the field of microbiology because diseases caused by helminths involve microscopic eggs and larvae. Viruses are acellular microorganisms, which means they are not composed of cells. Essentially, a virus consists of proteins and genetic material—either DNA or RNA, but never both—that are inert outside of a host organism. However, by incorporating themselves into a host cell, viruses are able to co-opt the host’s cellular mechanisms to multiply and infect other hosts. Viruses can infect all types of cells, from human cells to the cells of other microorganisms. In humans, viruses are responsible for numerous diseases. However, many viruses do not cause disease. By definition, microorganisms, or microbes, are very small organisms; many types of microbes are too small to see without a microscope, although some parasites and fungi are visible to the naked eye. Fermentation is a process that uses bacteria, mold, or yeast to convert sugars (carbohydrates) to alcohol, gasses, and organic acids Smallpox was declared eradicated in 1980 due to global coordination and vaccine administration. HIV still has not been eliminated due to barriers in medication access and difficulties in vaccine development. The rise of microorganisms resistant to current treatment options is a major concern and research and development of new vaccines and treatments are necessary to continue preventing deaths caused by infectious disease. The microbiome consists of all microorganisms which live on or inside the human body. The microbiome consists of bacteria, fungi, and viruses. Most members of the human microbiome are nonpathogenic. Different populations of microbes live in different body locations. Some play an important role like helping to digest food or creating vitamins humans cannot make on their own while others merely help prevent infection from pathogens by making it harder for pathogens to outcompete the microbiota efficiently enough to cause infection. Other impacts of the microbiome include impacts on the development of the immune system, neurological disorders, weight gain and loss, Microorganism/Microbe: an organism of microscopic size which requires a microscope to be viewed Examples: bacteria, fungi, protozoa, microscopic algae, and viruses Medical Microbiology/Clinical Microbiology: The study of microorganisms responsible for human disease Pathogen: microbes capable of causing disease Examples: Covid-19, E. coli, Candida albicans, Plasmodium parasite Pathogenesis: the process by which pathogens infect and cause disease Microbiologists: ● Identify pathogens using characteristics ● Identify novel (new) pathogens ● Collect and analyze data about pathogens, microbiome, and disease ● Learn details of the characteristics of pathogens ● Develop treatments for diseases caused by pathogens ● Research impacts of microbiome and how they impact health ● Develop vaccines against pathogens ● ● ● Identify origin of pathogen Develop strategies to decrease/eliminate new infections ○ Killing mosquitoes to fight Zika ○ Handwashing campaigns ○ Mandatory vaccines ○ Inform public health departments of steps to take to protect population from disease Work with other biomedical scientists to understand harm to different tissues and organs caused by pathogen Ancient peoples attempted to stop the spread of disease through: ● Using antimicrobial compounds such as honey, onion, and garlic ● Quarantine: keeping those sick with diseases like leprosy away from others ● Clean drinking water systems ● Keeping waste water separate from drinking water Indus-Valley Civilization in Modern Pakistan has oldest discovered public sanitation system in world from 2500 BCE (about 4,500 years ago) Hippocrates is considered the father of medicine but received training in Egypt. Hippocrates rejected the idea that disease was caused by the supernatural instead claiming disease comes from within the patient or their environment. Thucydides is called the father of scientific history and pushed for evidence-based analysis of cause-and-effect reasoning Thucydides made important observations of the Athenian plague and put forth the idea of immunity, ie people do not tend to get re-infected by the same disease Marcus Terentius Varro was a Roman writer suggested that diseases can be caused by things we cannot see Abū Bakr al-Rāzī used experiments to test and develop medicine Canon of Medicine was compiled by Ibn Sina in 1025 CE and built off of knowledge from ancient Egypt, Greece, Rome, China, and India. Some major breakthroughs of this work which was translated into many languages and used to teach doctors for centuries are: Infections can be spread through breathing, Organisms can be infected by foreign substances, isolation of those who are sick to prevent spread of infection, organizing illnesses by body part affected and listed treatments for different diseases. Antonie van Leeuwenhoek developed lenses powerful enough to view microorganisms Louis Pasteur ● Demonstrated fermentation is caused by microorganisms ● ● ● Different microbial strains have different properties Invented pasteurization the process of killing microbes in foods to prevent spoilage Developed multiple vaccines Robert Koch was the First to demonstrate specific microbe cause specific diseases