Novel Processes for Anaerobic Sulfate Production from Elemental Sulfur by Sulfate-Reducing Bacteria

Abstract

Sulfate reducers and related organisms which had previously been found to reduce Fe(III) with H2 or organic electron donors oxidized So to sulfate when Mn(IV) was provided as an electron acceptor. Organisms catalyzing this reaction in washed cell suspensions included Desulfovibrio desulfuricans, Desulfomicrobium baculatum, Desulfobacterium autotrophicum, Desulfuromonas acetoxidans, and Geobacter metallireducens. These organisms produced little or no sulfate from S with Fe(III) as a potential electron acceptor or in the absence of an electron acceptor. In detailed studies with Desulfovibrio desu(/i4ricans, the stoichiometry of sulfate and Mn(II) production was consistent with the reaction S + 3 MnO2 + 4H ,->SO42-+ 3Mn(II) + 2H20. None of the organisms evaluated could be grown with S as the sole electron donor and Mn(IV) as the electron acceptor. In contrast to the other sulfate reducers evaluated, Desulfobulbus propionicus produced sulfate from So in the absence of an electron acceptor and Fe(III) oxide stimulated sulfate production. Sulfide also accumulated in the absence of Mn(IV) or Fe(III). The stoichiometry of sulfate and sulfide production indicated that Desulfobulbus propionicus disproportionates S as follows: 45 + 4H20-,SO42-+ 3HS-+ 5 HW. Growth of Desulfobulbus propionicus with So as the electron donor and Fe(III) as a sulfide sink and/or electron acceptor was very slow. The S oxidation coupled to Mn(IV) reduction described here provides a potential explanation for the Mn(IV)-dependent sulfate production that previous studies have observed in anoxic marine sediments.

Fate of elemental sulfur in an intertidal sediment

“…With the addition of Mn oxides, sulfide produced during the disproportionation is rapidly reoxidized to S", so the net stoichiometry is the same as with direct S" oxidation to SOi- (Table 1; [15]). More recently, the sulfatereducing bacterium Desulfobulbus propionicus was shown to disproportionate S" anaerobically to sulfide and SO:-in the presence of Fe oxides [9], in the same manner as previously described [15], but only with poor growth.…”

“…The intermediates S", SO:-and S20z-may also be oxidized, as for example by Desulfouibrio desuljiuricans, with 0, as the electron acceptor [S]. Sulfate-reducing bacteha have also been reported to catalyze S" oxidation to SO:-with manganese oxide [9]. D.E.…”

Free‐living chemoautotrophic and particle‐attached heterotrophic prokaryotes dominate microbial assemblages along a pelagic redox gradient

“…Particle-associated microbes in a redox gradient 703 disproportionate sulfur intermediates or oxidize reduced sulfur (Lovley and Phillips, 1994). d-Proteobacterial sulfate reducers have previously been identified in the Cariaco Basin but were absent or in very low abundance at shallow anoxic depths near the interface (Madrid et al, 2001;Lin et al, 2006;Rodriguez-Mora et al, 2013;.…”

Diversity and vertical distribution of cultured and uncultured Deltaproteobacteria in an intertidal mud flat of the Wadden Sea

“…Sulfate-reducing prokaryotes (SRP) are metabolically highly diverse, and have been shown to be abundant in marine sediment (Devereux et al , 1992;Ravenschlag et al , 2000). They share the capability to reduce sulfate, but may also reduce alternative electron acceptors such as nitrate, iron and manganese oxides, sulfur and even oxygen (Szewzyk and Pfennig, 1987;Dannenberg et al , 1992;Lovley and Phillips, 1994). Concurrently, they oxidize various organic and inorganic compounds (Widdel and Bak, 1992;Rabus et al , 2000 ).…”