What is the oxidation state and name of S2-?
Sulfide, mercaptans
ox.state: -2
What is the oxidation state and name of S0
Elemental sulfur
0
What is the name and oxidation state of S2O4?
Hyposulfur
+2
What is the name and oxidation state of SO3 2-
Sulfite
+4
What is the name and oxidation state of SO4 2-
Sulfate
+6
What is desulfuration?
R-SH => H2S
Decomposition of organic matter: yields H2S
Recycling of organosulfur compounds
What is Sulfur respiration? In what condition does it happen?
Anaerobic condition
Reduction of S0 as terminal electron acceptor via anaerobic respiration (many species) : yields H2S
What is sulfide and sulfur oxidation? What conditions?
Aerobic conditions
Ocidation of H2S and S0 , with O2 as TEA in energy generation
What are examples of organisms that do sulfide and/or sulfur oxidation?
Bacteria
BEGGIATOA and THIOTHRIX (sulfur bacteria) => can oxidize H2S and accumulate S0 intracellularly
- Some species oxidize S0 to SO4 2-
Archea
SULFOLOBUS oxidizes S0, yiedling sulfuric acid
Chemolitotrophs => ACIDITHIOBACILLUS THIOOXIDANS
- (recall microbial oxidation of sulfidic ores results in sulfuric acid etc, production causing acid mine drainage)
What is Chemotrophic oxidation of sulfide and sulfur? in what conditions?
Anaerobic conditions
H2S=> S0 => SO4 2-
- Oxidation of sulfides or sulfur with electron acceptors other than oxygen (anaerobic respiration) : yields S0 or SO4 2-
Give example of organism doing chemotrophic oxidation of sulfide and sulfur
THIOMARGARITA and BEGGIATOA can use H2S as energy source with NO3- as TEA
What is phototrophic oxidation of sulfide and sulfur? What conditions?
Anaerobic
Use sulfides or S0 as e- donor => yields S0 or SO4 2-
Similar to oxidation of H2O => H2 + O2 in oxygenic P/S
What are examples of organisms doing phototrophic oxidation of sulfide and sulfur?
Chromatium (purple sulfur)
Chlorobium (green sulfur)
Describe sulfate assimilation
Assimilatory sulfate reduction (done by many species)
- Similar to assimilatory nitrate reduction
- As cells only need a relatively very small amount of S this pathway is tightly regulated
Formation of a.a. (cys and met)
- Assimilatory pathway is subject to end-product inhibition - Dissimilatory sulfate reduction (like dissimilatory nitrate reduction) is not subject to end-product inhibition
What is dissimilatory sulfate reduction?
-Sulfate reducing bacteria (SRBs)
=> Desulfovibrio
- Use SO4 20 as terminal electron acceptor in anaerobic respiration
- Use H2 and/or organic carbon as energy and electron source
- H2S prouced is an important energy and electron source for other microorganisms
Explain what is biological deposition of elemental sulfur? What are the 2 types of deposition?
S0 deposits form in lakes and geological formations
- Desulfovibrio, Thiobacillus, Chlorobium
- Initiated by dissimilatory sulfate reduction to H2S by SRBs such as Desulfovibrio
Oxidation of H2S to So in aquatic and geological environments (aerobically or anaerobically) contributes to S0 deposits
2 types:
Sulfur deposition via AEROBIC CHEMOTROPHIC sulfide oxidation
-H2S can be oxidized to S0 by Thiobacillus
Sulfur deposition via ANAEROBIC PHOTOTROPHIC sulfide oxidation
- H2S can be oxidized to S0 by phototrophs such as Chlorobium, providing there is is light
