Transcript Sulfur Cycling - Penn State York

Sulfur Cycle Facts
• Sulfur Oxidation States
–
–
–
–
–
Sulfide and organic sulfhydryl groups =
Elemental sulfur =
Thiosulfate (S2O3-2) =
Sulfite (SO3-2) =
Sulfate (SO4-2) =
-2
0
+2
+4
+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.
Global Input
and Outputs
Sulfur Cycling
Sº
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
Protocooperation
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 Oxidizers
Like 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 pachyptila Giant Tube Worms …
Microbial Mats
(No not me!)
Coral Disease (e.g. BBD)
Black Band Disease’s
mobile microbial mat community
DEAD CORAL
Phormidium corallyticum
Spread rate
~1 cm/d
LIVE CORAL
Beggiatoa spp.