Dissimilatory Sulfate Reducers (SRBs)
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Transcript of Dissimilatory Sulfate Reducers (SRBs)
Dusty Berggren07.22.10
Dissimilatory Sulfate Reducers(SRBs)
IntroductionSulfate reducers…
reduce sulfate to sulfide (8 e- transferred total)are strict anaerobescan 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)
23
][224 )( SOAPSsulfateinephosphoAdenosSO
reductaseAPS
H
esulfurylasATP
ATP
HSHSOreductaseBisulfite
H ][63
GGoo’ = -44.5 ’ = -44.5 kJ/molkJ/mol
If ATP If ATP 2P 2Pii
Desulfovibrio sapovorans
www.microbiological-garden.net
EnrichmentsComponent Purpose
--Basal Marine Mineral Media --
Na2SO4 (30 mM) Electron Acceptor
Sodium Lactate (10 mM)
Electron Donor
Resazurin (x 1000)
Anaerobic Indicator
NaHCO3 (30 mM) pH Buffer
7 Vitamin-Solution
Vitamins for growth
SL 10Trace Element Solution
Na2S (1 mM)
Reductant to maintain anaerobic conditions
pH 7.2
Inoculate 50 mL Pfennig bottles with sediment sample
Store in dark at 30oCMonitor development
of sulfide smell (<3 days)
Observe microscopically
Transfer ~3 mL liquid to new media bottle when necessaryEnrich by dilution
EnrichmentsComponent Purpose
--Basal Marine Mineral Media --
Na2SO4 (30 mM) Electron Acceptor
Sodium Lactate (10 mM)
Electron Donor
Resazurin (x 1000)
Anaerobic Indicator
NaHCO3 (30 mM) pH Buffer
7 Vitamin-Solution
Vitamins for growth
SL 10Trace Element Solution
Na2S (1 mM)
Reductant to maintain anaerobic conditions
pH 7.2
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
The Poor-Man’s SRB Picture
The Rich-Man’s SRB Picture
MorphologyGeneral
Consensus…
Sulfate reducers aren’t very fun to take pictures of.
--Small rods or ‘blobs’--
Further Enrichment Agar Shakes
Deep Agar Dilution Series “Shakes”
3 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