16 Notes - Topic 16 Fundamentals of Microbiology...

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Unformatted text preview: Topic 16 Fundamentals of Microbiology (Biology 140) Course notes Dr. Josh D. Neufeld Learning Objectives: To understand the categories of Gram ­negative Bacteria within the Proteobacteria. We have now seen how the life forms that exist on Earth today are evolutionarily related. While taxonomy of the Bacteria and Archaea is continually maturing, a current view of the taxonomy (as found in Bergey's Manual) is shown in Appendix 2 of your textbook. In the next few lectures, we will look at several examples of the substantial diversity of microbial life. We will see where these organisms live, and how they make their living. We will begin considering a few phylogenetic groups of the bacteria (Figure 17.1), starting with the Proteobacteria (Table 17.2), which metabolically and morphologically diverse Gram ­negative organisms. Purple Phototrophic Bacteria • Anoxygenic photosynthesis • O2 inhibits photosynthesis, but some can grow aerobically using respiration. • Bacteriochlorophylls and carotenoid pigments (Figure 17.3) determine which wavelengths of light are used for photosynthesis. • Lamellae (flat membrane sheets) and vesicles are used for pigment insertion (Figure 17.4). Purple Sulfur Bacteria (Table 17.1) • Photoautotrophs, oxidize H2S to S0 during photosynthetic CO2 reduction • S0 is stored in periplasm • Found in anoxic zones of lakes where H2S present Purple Nonsulfur Bacteria (Table 17.2) • Only very low levels of H2S oxidation • Photoheterotrophs (can use light for energy and organic compound for carbon) • N2 fixers Fundamentals of Microbiology (Biology 140) Course notes Dr. Josh D. Neufeld Methanotrophs (Tables 17.6 and 17.7) • Only organisms which are able to oxidize methane and other C1 compounds which lack carbon ­carbon bonds • Are unable to utilize compounds which contain carbon ­carbon bonds • Contain the enzyme methane monooxygenase, which is used to convert methane to methanol • Obligate aerobes • In nature, often found at the thermocline between anoxic zones, where methane is formed, and oxic zones, where O2 is available for respiration • Some methanotrophs are symbionts of marine mussels that live near geological sources of methane (Figure 17.15), and are found in mussel lung tissue Nitrifiers (Figure 17.8) • Oxidize ammonia (Nitrosococcus and Nitrosomonas) or nitrite (Nitrobacter) • Strict aerobes • Chemolithoautotrophs • Widespread distribution: found in wastewater treatment plants, soils, lakes, sediments. Pseudomonads (Tables 17.8 and 17.9) • Very heterogeneous group, taxonomy has been revised recently • Aerobic chemoorganotrophs, nutritionally versatile, polar flagella • Inhabit many different environments (e.g. soil, water, animal pathogens, plant pathogens) Fundamentals of Microbiology (Biology 140) Course notes Dr. Josh D. Neufeld Free Living Aerobic N2 ­Fixing Bacteria (Table 17.10) • Strict aerobes • Able to fix N2 aerobically, although the nitrogenase enzyme, which reduces N2 to NH3, is irreversibly inactivated by O2 • Have thick slime layer (Figure 17.19) and very high rate of respiration, which together keep the intracellular O2 concentration low during N2 fixation • e.g. Azotobacter (cysts; resting vegetative cells) Enteric Bacteria (Table 17.12) • e.g. Escherichia coli, Salmonella • All within the Gammaproteobacteria • More closely related than justified by genus ­level groupings • Peritrichous flagella, facultative, oxidase negative, simple nutritional requirements (Table 17.12) • Includes many pathogens, therefore very well studied • Genera can be separated by diagnostic tests (Tables 17.12, Figure 17.23) Rickettsias • Cell morphology can be quite variable (cocci to rods) • Most obligate intracellular parasites • Arthropod vectors • Ancestral mitochondria likely closest to ancestral Rickettsia species ...
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This note was uploaded on 12/23/2011 for the course BIOL 140 taught by Professor Dr.joshneufeld during the Fall '10 term at Waterloo.

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