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Sulfur Cycle Facts. Sulfur Oxidation States Sulfide and organic sulfhydryl groups = -2 Elemental sulfur = 0 Thiosulfate (S 2 O 3 -2 ) = +2 Sulfite (SO 3 -2 ) = +4 Sulfate (SO 4 -2 ) = +6 Sources of sulfur to the global cycle? Weathering & volcanism & sea-spray
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Sulfur Cycle Facts • Sulfur Oxidation States • Sulfide and organic sulfhydryl groups = -2 • Elemental sulfur = 0 • Thiosulfate (S2O3-2) = +2 • Sulfite (SO3-2) = +4 • Sulfate (SO4-2) = +6 • Sources of sulfur to the global cycle? • Weathering & volcanism & sea-spray • Biological emission of Dimethyl Sulfide (DMS) from oceans. • Fossil fuel combustion (photo-oxidation of SO2). • Most sulfur is in seawater and sedimentary rocks. • Assimilatory sulfate reduction: • Incorporates sulfate into methionine and cystein (amino acids). • Only some anaerobes assimilate S-2 directly to organic matter.
Sulfur Cycling Sº Desulfuromonas
Hypereutrophic Lakes • Very high primary production at the surface and thermocline. • Organic particles sink to hypolimnion and sediments, which have become anaerobic by summer due to stratification. • Anaerobic decomposition will release sulfide by desulfurylation and sulfate reducing bacteria; the later is more dominant with increasing sulfate of Sº supply. • Diffusion of sulfide to illuminated water supports anoxygenic phototrophy and Sº . • Diffusion of sulfide to microaerobic zone supports SOB and Sº. Sº
Lake Fryxell • Appearances are similar. • Although reverse stratification. • Sulfide source from the bottom and oxygen at the “surface”. • Why no sulfur phototrophs? • - purple sulfur (Chromatium) • - green sulfur (Chlorobium) • How does the S-cycle complete itself?
Sulfide OxidizersLike IOBs, these SOBs favor microaerobic conditions and may be isolated by gradient tubes. What about SOAs (A=archaea)?
Symbiotic Sulfide Oxidizing Bacteria Infers protection of animal tissues from toxic sulfides. Animal feeds off of the organic matter produced by these chemolithoautotrophs. There’s a happy marine nematode woven inside this filamentous SOB!
Endosymbiotic SOB of marine invertebrates Solemya velum, the Atlantic Awningclam is a salt marsh clam without feeding gills. Riftia pachyptilaGiant Tube Worms …
Black Band Disease’s mobile microbial mat community DEAD CORAL Phormidium corallyticum Spread rate ~1 cm/d LIVE CORAL Beggiatoa spp.