1. 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 –Biological emission of Dimethyl Sulfide (DMS) from oceans. –Fossil fuel combustion (photo-oxidation of SO 2 ). 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.

2. Global Input and Outputs

3. Sulfur Cycling SºSº Desulfuromonas

4. 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. SºSº

5. Protocooperation

6. 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?

7. Sulfide Oxidizers Like IOBs, these SOBs favor microaerobic conditions and may be isolated by gradient tubes. What about SOAs (A=archaea)?

8. 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!

9. Endosymbiotic SOB of marine invertebrates Solemya velum, the Atlantic Awningclam is a salt marsh clam without feeding gills. Riftia pachyptila Giant Tube Worms …Giant Tube Worms

11. Microbial Mats (No not me!)

13. Coral Disease (e.g. BBD)BBD

14. Black Band Disease’s mobile microbial mat community Phormidium corallyticum Beggiatoa spp. LIVE CORAL DEAD CORAL Spread rate ~1 cm/d