Publications

• Thiosulfate reduction in Salmonella enterica is driven by the proton motive force.

  Stoffels L., Krehenbrink M., Berks B.C., Unden G.

  Thiosulfate respiration in Salmonella enterica serovar Typhimurium is catalyzed by the membrane-bound enzyme thiosulfate reductase. Experiments with quinone biosynthesis mutants show that menaquinol is the sole electron donor to thiosulfate reductase. However, the reduction of thiosulfate by menaq ... >> More

  Thiosulfate respiration in Salmonella enterica serovar Typhimurium is catalyzed by the membrane-bound enzyme thiosulfate reductase. Experiments with quinone biosynthesis mutants show that menaquinol is the sole electron donor to thiosulfate reductase. However, the reduction of thiosulfate by menaquinol is highly endergonic under standard conditions (ΔE°' = -328 mV). Thiosulfate reductase activity was found to depend on the proton motive force (PMF) across the cytoplasmic membrane. A structural model for thiosulfate reductase suggests that the PMF drives endergonic electron flow within the enzyme by a reverse loop mechanism. Thiosulfate reductase was able to catalyze the combined oxidation of sulfide and sulfite to thiosulfate in a reverse of the physiological reaction. In contrast to the forward reaction the exergonic thiosulfate-forming reaction was PMF independent. Electron transfer from formate to thiosulfate in whole cells occurs predominantly by intraspecies hydrogen transfer. << Less

  J. Bacteriol. 194:475-485(2012) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• The phs gene and hydrogen sulfide production by Salmonella typhimurium.

  Clark M.A., Barrett E.L.

  Salmonella typhimurium produces H2S from thiosulfate or sulfite. The respective pathways for the two reductions must be distinct as mutants carrying motations in phs, chlA, and menB reduced sulfite, but not thiosulfate, to H2S, and glucose repressed the production of H2S from thiosulfate while it ... >> More

  Salmonella typhimurium produces H2S from thiosulfate or sulfite. The respective pathways for the two reductions must be distinct as mutants carrying motations in phs, chlA, and menB reduced sulfite, but not thiosulfate, to H2S, and glucose repressed the production of H2S from thiosulfate while it stimulated its production from sulfite. The phs and chlA mutants also lacked a methyl viologen-linked thiosulfate reductase activity present in anaerobically grown wild-type cultures. A number of hydroxylamine, transposon Tn10 insertion, and Mu d1(Apr lac) operon fusion mutants defective in phs were characterized. One of the hydroxylamine mutants was an amber mutant, as indicated by suppression of its mutation in a supD background. The temperature-sensitive phs mutants produced H2S and methyl viologen-linked thiosulfate reductase at 30 degrees C but not at 42 degrees C. The reductases in all such mutants grown at 30 degrees C were as thermostable as the wild-type enzyme and did not differ in electrophoretic relative mobility, suggesting that phs is not the structural gene for thiosulfate reductase. Expression of beta-galactosidase in phs::Mu d1(Apr lac) mutants was dependent on anaerobiosis and the presence of reduced sulfur. It was also strongly influenced by carbon source and growth stage. The results are consistent with a model in which the phs gene encodes a regulatory protein essential for the reduction of thiosulfate to hydrogen sulfide. << Less

  J. Bacteriol. 169:2391-2397(1987) [PubMed] [EuropePMC]

• Map locations and functions of Salmonella typhimurium men genes.

  Kwan H.S., Barrett E.L.

  Menaquinone (men) mutants of Salmonella typhimurium isolated on the basis of their inability to produce trimethylamine were characterized with respect to mutation site, the ability to cross-feed each other and be cross-fed by known Escherichia coli men mutants, and response to intermediates of the ... >> More

  Menaquinone (men) mutants of Salmonella typhimurium isolated on the basis of their inability to produce trimethylamine were characterized with respect to mutation site, the ability to cross-feed each other and be cross-fed by known Escherichia coli men mutants, and response to intermediates of the menaquinone biosynthetic pathway. Cross-feeding tests were based on the requirement of menaquinone for hydrogen sulfide production. Genotypes corresponding to the menA, B, C, D, and possibly E genes described in E. coli were all identified. Additional studies of deletions in the menBCD area revealed that this cluster lies between ack/pta and glpT, as in E. coli. The ack and pta mutants were also defective in the production of trimethylamine and failed to produce gas in the absence of added formate. << Less

  J Bacteriol 159:1090-1092(1984) [PubMed] [EuropePMC]

• Sequence analysis of the phs operon in Salmonella typhimurium and the contribution of thiosulfate reduction to anaerobic energy metabolism.

  Heinzinger N.K., Fujimoto S.Y., Clark M.A., Moreno M.S., Barrett E.L.

  The phs chromosomal locus of Salmonella typhimurium is essential for the dissimilatory anaerobic reduction of thiosulfate to hydrogen sulfide. Sequence analysis of the phs region revealed a functional operon with three open reading frames, designated phsA, phsB, and phsC, which encode peptides of ... >> More

  The phs chromosomal locus of Salmonella typhimurium is essential for the dissimilatory anaerobic reduction of thiosulfate to hydrogen sulfide. Sequence analysis of the phs region revealed a functional operon with three open reading frames, designated phsA, phsB, and phsC, which encode peptides of 82.7, 21.3, and 28.5 kDa, respectively. The predicted products of phsA and phsB exhibited significant homology with the catalytic and electron transfer subunits of several other anaerobic molybdoprotein oxidoreductases, including Escherichia coli dimethyl sulfoxide reductase, nitrate reductase, and formate dehydrogenase. Simultaneous comparison of PhsA to seven homologous molybdoproteins revealed numerous similarities among all eight throughout the entire frame, hence, significant amino acid conservation among molybdoprotein oxidoreductases. Comparison of PhsB to six other homologous sequences revealed four highly conserved iron-sulfur clusters. The predicted phsC product was highly hydrophobic and similar in size to the hydrophobic subunits of the molybdoprotein oxidoreductases containing subunits homologous to phsA and phsB. Thus, phsABC appears to encode thiosulfate reductase. Single-copy phs-lac translational fusions required both anaerobiosis and thiosulfate for full expression, whereas multicopy phs-lac translational fusions responded to either thiosulfate or anaerobiosis, suggesting that oxygen and thiosulfate control of phs involves negative regulation. A possible role for thiosulfate reduction in anaerobic respiration was examined. Thiosulfate did not significantly augment the final densities of anaerobic cultures grown on any of the 18 carbon sources tested. on the other hand, washed stationary-phase cells depleted of ATP were shown to synthesize small amounts of ATP on the addition of the formate and thiosulfate, suggesting that the thiosulfate reduction plays a unique role in anaerobic energy conservation by S typhimurium. << Less

  J. Bacteriol. 177:2813-2820(1995) [PubMed] [EuropePMC]

• Cloning and characterization of a gene cluster, phsBCDEF, necessary for the production of hydrogen sulfide from thiosulfate by Salmonella typhimurium.

  Alami N., Hallenbeck P.C.

  We cloned, by complementation of an H2S-mutant, a cluster of Salmonella typhimurium genes, phsBCDEF, that appears to be essential for the anaerobic production of hydrogen sulfide from thiosulfate. Tn5 mutagenesis and ExoIII deletion analysis showed that approx. the entire region of a 3.3-kb subclo ... >> More

  We cloned, by complementation of an H2S-mutant, a cluster of Salmonella typhimurium genes, phsBCDEF, that appears to be essential for the anaerobic production of hydrogen sulfide from thiosulfate. Tn5 mutagenesis and ExoIII deletion analysis showed that approx. the entire region of a 3.3-kb subclone was necessary for H2S production. Subsequent sequencing revealed the presence of five potential translationally coupled open reading frames (ORFs). Their putative protein products were confirmed by synthesis from a phage T7 expression system. Comparison of the encoded sequences with previously determined sequences suggests that these genes constitute part of a thiosulfate-reducing operon coding for a membrane-associated electron transport chain which contains proteins potentially capable of ligating iron-sulfur clusters and heme. Immediately upstream from these genes, a region encoding the C-terminal portion of an ORF (OrfA) was identified that showed a high degree of similarity to some other anaerobic terminal reductases, polysulfide reductase (PsrA) of Wolinella succinogenes and dimethylsulfoxide reductase (DmsA), formate dehydrogenase (formate-hydrogene-lyase linked) (FdhF) and nitrate reductase (NarG) of Escherichia coli. << Less

  Gene 156:53-57(1995) [PubMed] [EuropePMC]