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Anoxygenic Phototrophs

Anoxygenic Phototrophs. What are they?. Photosynthetic bacteria which use a reducing agent and light energy to build organic material, but do not produce oxygen Use bacteriochlorophyll to accomplish photosynthesis – specific to each type of bacteria Starch (carbohydrate) is a main product.

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Anoxygenic Phototrophs

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  1. Anoxygenic Phototrophs

  2. What are they? • Photosynthetic bacteria which use a reducing agent and light energy to build organic material, but do not produce oxygen • Use bacteriochlorophyll to accomplish photosynthesis – specific to each type of bacteria • Starch (carbohydrate) is a main product

  3. Bacteriochlorophyll • 6 types: a,b,c,d,e,g • C & D are chlorins (1 reduced pyrrole ring), others are bacteriochlorins (2 reduced rings) • Chlorin – heterocyclic aromatic ring with 3 pyrroles at the center • Photosynthetic pigment related to chlorophyll

  4. Chlorin Bacteriochlorin: 2 reduced pyrroles Chlorin: 1 reduced pyrrole

  5. Types • Proteobacteria, ie: purple bacteria • Green sulfur bacteria • Green non-sulfur bacteria • Heliobacteria

  6. Proteobacteria: Purple Bacteria • Gram negative, non-sporing, non acid fast, varying morphologies • Pigmented with bacteriochlorophyll a or b & carotenoids (organic pigments) • Anoxygenic type II photosynthesis in rxn centers on cell membranes • Reducing agent is sulfur or hydrogen • CO2 + 2H2S  CH2O + H2O + 2S

  7. Purple Sulfur Bacteria - Chromatiaceae Electron sources: Example: • Gamma type • Red/purple pigmentation from carotenoids

  8. Purple Non-sulfur BacteriaRhodospirillaceae • Alpha type • Photoorganoheterotroph • Use organic e- donors, simple organic molecules (instead of CO2), and light energy for metabolism • Genus Magnetospirillum contain tiny chains of magnetite • Allow them to sense the Earth’s magnetic field and orient themselves

  9. Rhosospirillum http://www.biol.tsukuba.ac.jp/~inouye/ino/bc/purple%20nonsulfur.html Rhodopseudomonas

  10. Green Non-sulfur Bacteria • Chloroflexus is major representative • Filamentous, gliding, and thermophilic • Isolated from neutral to alkaline hot springs • Resembles green sulfur bacteria in ultrastructure and photosynthetic pigment • Metabolism similar to that of purple non-sulfur

  11. Green Sulfur Bacteria • Have their own phylum: Chlorobi • Non-motile, except for one species • Can be baccilus, coccus, or spiralus • Environment must be free of oxygen • Use bacteriochlorophyll c,d,& e in chlorosome vesicles on cell membrane • Sulfide is reducing agent • Found in black smokers @ 2500 ft.

  12. Heliobacteria • Use bacteriochlorophyll g on cell membrane • Gram negative, endospore forming, obligate anaerobes • Common in dry environments, soil • Strong N-fixation  possible symbiotic relationship with plants

  13. Heliobacterium chlorum Heliobacterium modesticaldum http://et.springer-ny.com:8080/prokPUB/chaprender/jsp/showchap.jsp?chapnum=304

  14. Relatedness • Determined from 16s rRNA • Shows that they are more closely related to non-photosynthetic subgroups than each other

  15. Works Cited Lindquist, John – Dept. of Bacteriology, U. of Wisconsin - http://www.splammo.net/bact102/102pnsb.html MicroBioNet - http://www.microbionet.com.au/chromatiaceae.htm The Prokaryotes – Ed. Martin Dworkin, Department of Microbiology, of Minnesota http://et.springer-ny.com:8080/prokPUB/chaplist_organism_full.htm

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