MICROBIOLOGY PRELIMS

• Microorganisms, or microbes, are minute living things that individually are usually too small to be seen with the unaided eye.
• Microorganisms include Bacteria, Fungi (yeasts, molds), Protozoa, Microscopic Algae, and Viruses.
• The majority of microbes help maintain the balance of chemicals in the environment.
• Microbes form the base of the food chain in various areas of the environment.
• Larger bacterial cells lost their cell walls and engulfed smaller bacterial cells, a relationship called endosymbiosis.
• Alcohol and hydrogen peroxide are detoxified by the cell, protecting the cell in the process.
• The Endosymbiotic Theory explains the origin of eukaryotes from prokaryotes, pioneered by Lynn Margulis.
• Centrosomes are the area of origin of microtubules that will form the organizing center for the mitotic spindle, which is important in mitosis.
• Soil microbes help break down wastes and help in recycling chemical elements between soil, water, air, and living beings.
• Bacteria are single-celled organisms that are Prokaryotes, have no true nucleus, are enclosed in a cell wall made of peptidoglycan, reproduce thru binary fission, use organic chemicals for nutrition or may produce own nutrition, and have different forms/morphology.
• Archaea are single-celled organisms that are Prokaryotes similar to bacteria, if contain a cell wall, lack peptidoglycan, are often found in extreme environments, and actually look like typical bacteria.
• Fungi are Eukaryotic organisms with a cell wall composed of chitin, can be unicellular (e.g. yeasts) or multicellular (e.g. molds, mushrooms), and have a variety of shapes and live either freely or act as parasites.
• Protozoa are unicellular eukaryotic microbes that move by pseudopods, flagella, or cilia, amoebae move with pseudopods (cytoplasmic extensions), have a variety of shapes and live either freely or act as parasites, reproduce sexually or asexually, and have an important role in the balance of nature and food chain.
• Algae are photosynthetic eukaryotes with a cell wall composed of cellulose, are usually classified under plants, can be unicellular (e.g. euglena) or multicellular (e.g. kelp), are abundant in freshwater, saltwater and soil, and play an important role in the balance of nature and food chain.
• Eukaryotic flagella and cilia move in a wave-like manner, unlike the prokaryotic flagellum that rotates to propel.
• The plasma membrane is a phospholipid bilayer forming a thin layer enclosing the cytoplasm of the cell, containing phospholipids and proteins, no sterols.
• Gram positive bacteria have cell walls that consist of many layers of peptidoglycan, forming a thick, rigid structure.
• Passive processes in bacteria include diffusion and osmosis.
• Gram negative cell walls contain high concentration of enzymes and transporters.
• Gram positive bacteria contain Teichoic acids in their cell walls.
• Gram negative bacteria have cell walls that consist of one or a few layers of peptidoglycan and an outer membrane, and no teichoic acids.
• Inclusions in bacteria can be metachromatic granules, polychromatic granules, lipid inclusions, sulfur granules, carboxysomes, gas vacuoles, magnetosomes, and endospores.
• The cytoplasm is the substance inside the plasma membrane, comprised of 80% water and 20% compounds such as proteins, carbohydrates, lipids, and inorganic ions.
• Sporulation is the process of endospore formation within a vegetative cell, taking several hours.
• The bacterial chromosome is a single long continuous, frequently circularly arranged thread of double stranded DNA.
• Other eukaryotes do not have typical cell walls.
• The nucleoid is the region containing the bacterial chromosome, the cell’s genetic information.
• Eukaryotic cell walls are much simpler than those in prokaryotic cells, with plant cell walls being cellulose, fungal cell walls being chitin, and yeast cell walls being glucan and mannan.
• Prokaryotic ribosomes are cytoplasmic structures that function in protein synthesis, composed of two subunits each containing own ribosomal RNA: 30S subunit and 50S subunit.
• Viruses are obligate intracellular parasites that reproduce only using cellular machinery of organisms, are inert outside living hosts, are acellular, contain a nucleic acid core (DNA or RNA) surrounded by a protein coat, and have an important role in the balance of nature and food chain.
• Spontaneous Generation is the idea that living organisms could arise from nonliving matter.
• Cell Theory states that all living things are composed of cells that arise from preexisting cells.
• Biogenesis is the claim that living cells can arise only from preexisting living cells.
• Germ Theory of Disease considers the possibility that microorganisms might have similar relationships with plants and animals, that microorganisms or “germs” caused disease.
• The cell wall is a semirigid structure enclosing the cell, and is responsible for cell shape.
• Bacteria can have basic shapes such as spherical Coccus (pleural: cocci) meaning berries, rod-shaped Bacillus (pleural: bacilli) meaning little staffs, spirals (including vibrios, spirillas & spirochetes), and other shapes.
• Histones are special chromosomal proteins found in eukaryotes.
• Infectious disease is a disease in which pathogens invade a susceptible host, carrying out at least a part of its life cycle inside the host, resulting in disease.
• Motility is the ability of an organism to move by itself.
• Fimbriae and pili are hair-like appendages used for attachment and transfer of DNA to another bacterium.