Environmental Engineering Reference
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Figure 2 Model reflecting the organization of protein complexes associated with electron trans-
port and cell energetics in sulfate-reducing bacteria. Abbreviations are as follows:
Qmo ¼QmoABC complex, Qrc ¼QrcABCD complex, Dsr ¼DsrKMJOP complex,
Tmc ¼TmcABCD complex, Hmc ¼HmcABCDEF complex, ATP synthase ¼proton-driven
ATP synthase, Coo¼ carbon monoxide dehydrogenase-hydrogenase membrane complex system,
Ech¼multi-subunit membrane-bound hydrogenase, Fd¼ ferredoxin, Fdh¼ formate dehydroge-
nase, Hyd ¼ periplasmic [Fe] hydrogenase, Hyn ¼ periplasmic [NiFe] hydrogenase,
Hys ¼ periplasmic [NiFeSe] hydrogenase, Ohc ¼ octaheme cytochrome c membrane complex,
Rnf ¼ NADH:quinone oxidoreductase membrane complex, Tplc 3 ¼ periplasmic type I cyto-
chrome c 3 . Cytoplasmic enzymes are as follows: Ack ¼ acetate kinase, APSR ¼ adenylylsulfate
reductase, ATPS ¼ ATP sulfurylase, dSiR ¼ dissimilatory sulfite reductase, Ldh ¼ lactate dehy-
drogenase, Pfl ¼ pyruvate formate lyase, Por ¼ pyruvate:ferredoxin oxidoreductase, and Pta
phosphotransacetylase. Reproduced by permission from [ 25 ]; copyright 2012, Academic Press.
other possible terminal electron acceptors such as sulfate, sulfite, thiosulfate, nitrate
or nitrite. The growth of many species of SRB in the presence of sulfate is inhibited
by elemental sulfur, probably because sulfur as an oxidant shifts the potential of
redox couples in the medium and cells to unfavorable and positive values [ 3 ,
30 ]. Even if most of the SRB are not able to grow by dissimilatory elemental sulfur
reduction, some thiophilic species of SRB, belonging to fifteen genera (such as
Desulfomicrobium , Desulfovibrio , Desulfohalobium , Desulfosporosinus ,
Desulfotomaculum ) can use elemental sulfur as an alternative electron acceptor
(Table 1 )[ 25 , 37 - 39 ]. The eubacterial sulfur reducers comprise both facultative and
true (or strict) respiratory microorganims. Sulfur reducers use many different types
of metabolic systems for oxidizing organic compounds. Both complete and
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