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BIOL 140 Module 8 Notes

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BIOL 240
Trevor Charles

MODULE 8 Part A: The Proteobacteria Overview Phylogenic Overview - Proteobacteria  purple bacteria - Purple phototrophic bacteria are members - Other members: methanotrophs, Pseudomonas type organisms, free-living aerobic nitrogen-fixing organisms, Neisseria and its relatives, enteric bacteria The Proteobacteria - Proteobacteria divided into different groups  phylogenetic groupings based on 16S rRNA sequence - Many are photosynthetic - Gram-negative bacteria - Ancestral phototroph  delta purple, epsilon purple, gama purple, alpha purple and beta purple bacteria - Rhodo- bacteria  red - Pseudomonas  plant/human pathogens, non-pathogenic - Escherichia  human pathogen Purple Phototrophic Bacteria Overview - Microorganisms are pigmented - Carry out anoxygenic photosynthesis  no oxygen production - Oxygen inhibits photosynthesis  only in anaerobic conditions - Some can grow aerobically using respiration - No photosynthesis under aerobic conditions - Pigments  bacterial chlorophylls and carotenoids - Colour determines which wavelengths of light it can best absorb - Phototrophs  photoautotrophs (C = carbon dioxide) and Photoheterotrophs (C = organic) - Photosynthesis takes place in intracellular membrane folds Environment - Found in high H2S gas environments - H2S gas can be used as electron donor in CO2 reduction process - Below surface of lake water Purple Sulfur Bacteria - Photoautotrophs  oxidize H2S to elemental sulfur - Elemental sulfur stored in periplasm - Under anoxic conditions - All purple sulfur bacteria are members of gamma proteobacteria grouping Purple Nonsulfur Bacteria - No H2S oxidation - Some can carry out low level of H2S oxidation - Photoheterotrophs  carbon from organic sourse - Fix nitrogen - Members of alpha and beta proteobacteria grouping Methanotrophs Overview - Organism capable of oxidizing methane as an electron donor in energy metabolism - Methylotroph: capable of oxidizing compounds like methanol - Only organisms capable of oxidizing methane - Methane  C1 compound without C-C bond - Unable to utilize compounds containing C-C bonds - Restricted in types of environments they can inhabit - Methane monooxygenase  important enzyme – used in conversion of methane to methanol - Obligate aerobes – further restricting environments inhabited Environment - Biologically produced methane  anaerobic conditions but used by organisms with oxygen requirement - Methane diffuses from anoxic zone to oxic zone at thermocline - Region of sufficient oxygen and methane - Methane formed: ocean floor, rumen of cows and other ruminants, swamps and wetlands, anaerobic digesters of waste environemtn - Symbiotic interactions between marine mussles and methanotrophs Pseudomonads and Nitrogen-Fixing Bacteria Pseudomonads - Heterogenous group - Classified as aerobic chemoorganotrophs - Nutritionally versatile - Polar flagella - Different environments – soils, water, animal and plant pathogens Free Living Aerobic Nitrogen-Fixing Bacteria - Fix nitrogen under aerobic conditions while growing on their own in environment - Azotobacter  highest respiration rates and strict aerobes - Nitrogen fixation carried out by nitrogenase enzyme  ocygen sensitive - N-fixing organisms have interactions with hosts which shield them from high levels of oxygen or fix nitrogen anaerobically - Thick slime layer that coats cell - Oxygen diffuses into cell through slime layer but used at high rate that intracellular oxygen levels are low Neisseria and the Enteric Bacteria Neisseria - gram-negative cocci  causes gonorrhea - Non-motile and aerobic - Chromobacterium  members of this group with purple pigment violacein The Enteric Bacteria - All members of gamma proteobacteria grouping - Classical taxonomy and molecular phylogeny correspond - Peritrichous flagella - Facultative organisms - Oxidase negative Mixed Acid Fermentation cs. Butanediol Fermentation - Glucose  Pyruvate produces lactate, succinate, ethanol, a
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