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Unformatted text preview: 1 ESM 219 Nov 5 th : S, Fe, Hg cycles and microbes Microbes in the S cycle The global balance of sulfur. Artificial emissions are derived from human activities. An asterisk indicates a process that is partially or solely due to microbial action. NOTE: Biological and chemical S cycling are at similar rates. DMSO= dimethyl sulfoxide DMS = dimethyl sulfide Sulfur and sulfide oxidation sulfur oxidation (autrophic or heterotrophic) Lowers pH Thiobacillus are everywhere Beggiatoa mixotroph: organic cmpd for C, H 2 S for energy Oxidation reactions (can involve NO 3- ) S o + 3/2 O 2 + H 2 O H 2 SO 4-587 kJ/rxn H 2 S + 2O 2 SO 4 2- + 2H +-798.2 kJ/rxn HS- + O 2 + H + S o + H 2 O-209.4 kJ/rxn S 2 O 3 2- +H 2 O+2O 2 2SO 4 2- +2H +-822.6 kJ/rxn 2 Fates of DMS atmosphere release then photochemical oxidation in anoxic sys. is a substrate for methanogens e- donor to phototrophs yielding DMSO e- donor for chemolithotrophs or autotrophs Attachment of the sulfur-oxidizing archaeon Sulfolobus acidocaldarius to a crystal of elemental sulfur. Cells are visualized by fluorescence microscopy after staining the cells with the dye acridine orange. The sulfur crystal does not fluoresce. Deposition of internal sulfur granules by Beggiatoa. Sulfur and sulfate reduction Elemental sulfur can be reduced ( Archaeal ) Sulfate reduction to hydrogen sulfide SO 4 2- + 8H H 2 S + 2H 2 O + 2OH- Organic C oxidized, sulfate = e- acceptor Some can oxidize H 2 and acetate K s for H 2 6.6 M for methanogens 1.3 M for sulfate reducers K s for acetate 3 mM for methanogens 0.2 mM for sulfate reducers 0....
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This note was uploaded on 08/06/2008 for the course ESM 219 taught by Professor Holden during the Fall '07 term at UCSB.
- Fall '07