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Dusty Berggren 07.22.10 Dissimilatory Sulfate Reducers (SRBs)

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  • Dusty Berggren07.22.10Dissimilatory Sulfate Reducers(SRBs)

  • IntroductionSulfate reducers reduce sulfate to sulfide (8 e- transferred total)are strict anaerobescan act as syntrophsUse H2, formate, acetate, propionate, lactate, ethanol, butyrate as electron donorsOxidize 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/molIf ATP 2PiDesulfovibrio sapovoranswww.microbiological-garden.net

  • EnrichmentsInoculate 50 mL Pfennig bottles with sediment sampleStore in dark at 30oCMonitor development of sulfide smell (
  • EnrichmentsSelecting 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

    ComponentPurpose--Basal Marine Mineral Media --Na2SO4 (30 mM)Electron AcceptorSodium Lactate (10 mM)Electron DonorResazurin (x 1000)Anaerobic IndicatorNaHCO3 (30 mM)pH Buffer7 Vitamin-SolutionVitamins for growthSL 10Trace Element SolutionNa2S (1 mM)Reductant to maintain anaerobic conditionspH 7.2

  • The Poor-Mans SRB Picture

  • The Rich-Mans SRB Picture

  • MorphologyGeneral Consensus

    Sulfate reducers arent very fun to take pictures of.

    --Small rods or blobs--

  • Further Enrichment Agar Shakes

  • Deep Agar Dilution Series Shakes3 mL 3% Agar6 mL SRB Media~1 mL of culture/media from enrichment bottleAnoxic headspace

    Single colonies can be extracted and introduced to a Pfennig bottle with fresh SRB media for further purification

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