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Dissimilatory Sulfate Reducers (SRBs)

Dissimilatory Sulfate Reducers (SRBs). Dusty Berggren 07.22.10. Introduction. Desulfovibrio sapovorans. Sulfate reducers… reduce sulfate to sulfide (8 e - transferred total) are strict anaerobes can act as syntrophs

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Dissimilatory Sulfate Reducers (SRBs)

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  1. Dissimilatory Sulfate Reducers(SRBs) Dusty Berggren 07.22.10

  2. Introduction Desulfovibrio sapovorans • Sulfate reducers… • reduce sulfate to sulfide (8 e- transferred total) • are strict anaerobes • can act as syntrophs • Use H2, formate, acetate, propionate, lactate, ethanol, butyrate… as electron donors • Oxidize organic compounds to CO2 (complete) or a mixture of CO2 and acetate (incomplete) • can produce a hydrogen sulfide smell or FeS precipitates (black) DGo’ = -44.5 kJ/mol If ATP  2Pi www.microbiological-garden.net

  3. Enrichments • Inoculate 50 mL Pfennig bottles with sediment sample • Store in dark at 30oC • Monitor development of sulfide smell (<3 days) • Observe microscopically • Transfer ~3 mL liquid to new media bottle when necessary • Enrich by dilution

  4. Enrichments • Selecting for organisms that… • are anaerobes (facultative or obligate) • can utilize SO42- as an electron acceptor or ferment lactate • (SRBs or syntrophs… may be one in the same) • grow around neutral pH

  5. The Poor-Man’s SRB Picture

  6. The Rich-Man’s SRB Picture

  7. Morphology General Consensus… Sulfate reducers aren’t very fun to take pictures of. --Small rods or ‘blobs’--

  8. Further Enrichment Agar Shakes

  9. Deep Agar Dilution Series “Shakes” 3 mL 3% Agar 6 mL SRB Media ~1 mL of culture/media from enrichment bottle Anoxic headspace Single colonies can be extracted and introduced to a Pfennig bottle with fresh SRB media for further purification

  10. The Point? Knowing an organisms function aids its enrichment and purification through manipulation of the physical/chemical environment

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