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Summaries - 4 Proteobacteria: 1.- Phototrophes anoxygenic: a – Purple sulfur: Chromatium, Ectothiorhodospira, Thiocapsa b – Purple non-sulfur: Rhodospirillum, Rhodomicrobium 2.- Chemolithotrophs: a - Nitrosifyers & nitrifyers: Nitrosococcus, Nitrobacter b - Sulfur oxidizers: Thiobacillus, Beggiatoa, Thioploca c - Iron oxidizers: Leptothrix, Gallionella d - Hydrogen oxidizers e - Methane oxidizer 3.- Chemoorganotrophs: a - Aerobic respirers: Pseudomonads, Acetic A., N-fixers: Azotobacter, Photobacteria b - Anaerobic respirers: S - reducers, Desulfovibrio c - Facultative aerobes: Enteric bacteria, E. coli d - Fermenters: Zymomonas e - Pathogens: Neisseria, Campylobacter, Salmonella Vibrios, Spirilla, Prostecate bacteria, Myxobacteria Ammonia and nitrite can be used as electron donors by the nitrifying bacteria. The ammonia-oxidizing bacteria produce nitrite, which is then oxidized by the nitrite-oxidizing bacteria to nitrate. Anoxic NH3 oxidation is coupled to both N2 and NO3– production in the anammoxosome. Thiocapsa roseopersicina - a sulfide oxidizing, non-oxygenic phototroph containing intracellular sulfur grains and bundled tubular pigment vesicles So Purple bacteria are anoxygenic phototrophs that grow phototrophically, obtaining carbon from CO2 + H2S (purple sulfur bacteria) or organic compounds (purple nonsulfur bacteria). Purple nonsulfur bacteria are physiologically diverse and most can grow as chemoorganotrophs in darkness. The purple bacteria reside in the alpha, beta, and gamma subdivisions of the Proteobacteria. 3 – Cyanobacteria • Gram-negative bacteria (formerly blue-green ‘algae’) • Evolutionary origins and paleoecology of: Oxygenic phototrophy (unique event in evolution) All chloroplasts in eukaryotes through endosymbiosis Atmospheric oxygen provided by Cyanobacteria Most of the global primary production Stromatolites, organo-sedimentery structures • Ecological significance today: Dinitrogen fixation, respond to P-load as ‘algal blooms’ in coastal and interior waters and enrichment of tropical ocean (Trichodesmium) Picoplankton contribution to open ocean (Synechococcus, Prochlorococcus). Sediment and soil stabilization Microbial endoliths and bioerosion Microcystis flos aquae – a bloomForming, gas-vesicle loaded, Toxic coccoid cyanobacterium Petalonema alatum – a Heterocystous, N2-fixing, Filamentous cyanobacterium hν Phycoerythrin Phycocyanin Allophycocyanin Thylakoid membrane Chlorophyll a Phycobilisome Microbial Bioerosion Microbial bioerosion is carried by phototrophic cyanobacteria, green and red algae and organotrophic fungi. They may remove up to 50% of carbonate along the surfaces of substrates, such as shells, corals and limestone rocks. Solentia achromatica Endolithic cyanobacterium responsible for destruction of limestone coasts at the intertidal zone. Hyella racemus – a modern endolithic cyanobacterium and its Neoproterozoic counterpart Eohyella dichotoma After microbial endoliths have Successfully colonized the rock…… Microbial euendoliths are integrated in the community of prokaryotes and eukaryotes. Consequently, the combined bioerosion of microbial endoliths (bio-corrosion) and their grazers becomes a progressive force that undercuts limestone coasts, and creates sharp and bizarre shapes called ‘biokarst’. Biokarst & bioerosional notch are geologically significant Modifications of limestones caused by combined biocorrosion by microbial endoliths and bioabrasion by heir grazers detail Ammonia and nitrite can be used as electron donors by the nitrifying bacteria. The ammonia-oxidizing bacteria produce nitrite, which is then oxidized by the nitrite-oxidizing bacteria to nitrate. Anoxic NH3 oxidation is coupled to both N2 and NO3– production in the anammoxosome. Iron Bacteria They are chemolithotrophs able to use ferrous iron (Fe2+) as sole energy source. Most iron bacteria grow only at acid pH and are often associated with acid pollution from mineral and coal mining. Some phototrophic purple bacteria can oxidize Fe2+ to Fe3+ anaerobically. Methanotrophy & Methylotrophy Methane is oxidized by methanotrophic bacteria. Methane (CH4 ) is converted to methanol (CH3OH) by the enzyme methane monooxygenase (MMO). The electrons needed to drive this first step come from cytochrome c, and no energy is conserved in this reaction. A proton motive force is established from electron flow in the membrane, and this fuels ATPase. Carbon for biosynthesis comes primarily from formaldehyde (CH2O), MMO is a membraneassociated enzyme.