MODULE 8 - MODULE 8 8a1) The Proteobacteria: Overview...

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Unformatted text preview: MODULE 8 8a1) The Proteobacteria: Overview Phylogenetic Overview Proteobacteria: also known as the purple bacteria o Purple phototrophic bacteria are members of this group o Other members: methanotrophs, Pseudomonas type organisms, free-living aerobic nitrogen-fixing organisms, Neisseria and its relatives, Enteric bacteria Grouped into 5 groups, based on the sequence of the 16s rRNA o Alpha, beta, gamma, epsilon, delta Some of most well known microorganisms Gram-negative bacteria Many of the members of this grouping are photosynthetic (phototrophic) Ancestral phototroph at base of tree o Loss of photosynthetic ability in delta and epsilon Gammas: best known of any organisms o Includes number of human pathogens o Includes number of plant pathogens 8a2) Purple Phototrophic Bacteria Called purple b/c the microorganisms are often pigmented Pigments are important in photosynthesis Microorganisms are not green in colour b/c of a number of accessory pigments Carry out anoxygenic photosynthesis Oxygen inhibits photosynthesis so that these microorganisms only photosynthesize under anaerobic conditions Some members of this group can grow aerobically using repatriation There is no photosynthesis under aerobic conditions Pigments are bacterial chlorophylls and carotenoids Combination of these pigments gives each microorganism a distinct colour The colour determines which wavelengths of light it can best absorb The microorganisms are often adapted to specific light wavelengths Phototrophs: use light as an energy source o Photoautotroph: fix carbon dioxide to get carbon using energy obtained from photosynthesis o Photoheterotroph: get carbon from organic source Photosynthesis takes place in intracellular membrane folds Some purple phototrophic bacteria are found in high H 2 S gas environments o The gas can be used as an electron donor in the carbon dioxide reduction process Another habitat for these bacteria is below the surface of lake water Purple Sulfur Bacteria Photoautotrophs which oxidize H 2 S to elemental sulphur o Elemental sulphur is often stored in periplasm of these organisms o Organisms photosynthesize under anoxic conditions Fall under gamma Proteobacteria grouping Purple Nonsulfur Bacteria Do not carry out H 2 S oxidation Some examples of members o this group that can carry out low level of H 2 S oxidation Photoheterotrophs b/c they have to get their carbon from an organic source A number of these organisms can also fix nitrogen Fall under alphas and betas Proteobacteria grouping 8a3) Methanotrophs Overview Capable of oxidizing methane as an electron donor in energy metabolism Methylotroph: capable of oxidizing compounds like methanol Methanotrophs are the only organisms that can oxidize methane Methane is a C1 compound that does not have a carbon carbon bond Very restricted in their metabolism, unable to utilize compounds containing C-C...
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This note was uploaded on 06/26/2011 for the course BIOL 140 taught by Professor Dr.joshneufeld during the Winter '10 term at Waterloo.

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MODULE 8 - MODULE 8 8a1) The Proteobacteria: Overview...

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