Thiosulfate Reduction in Salmonella enterica Is Driven by the Proton Motive Force

Abstract

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 (⌬E°= ‫؍‬ ؊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.

Isolation of Salmonella enterica Serovar Kentucky Strain ST 198 and Its H 2 S-Negative Variant from a Patient: Implications for Diagnosis

“…A cofactor for the activity of thiosulfate reductase is molybdopterin guanine dinucleotide molybdenum (MGD) (8). It consists of molybdenum covalently bound to two sulfur atoms of a tricyclic pterin moiety, molybdopterin (9). In isolate 915, we found an insertion of a G in the moaC gene causing a frameshift mutation.…”

Genomic reconstruction of a novel, deeply branched sediment archaeal phylum with pathways for acetogenesis and sulfur reduction

“…Thiosulfate reductase preferentially utilizes thiosulfate as an electron acceptor. Thiosulfate is a dominant sulfur oxidation product in marine sediments (Jørgensen, 1990) and can be used as a substrate for both oxidation and reduction; microorganisms that reduce this important intermediate in the sulfur cycle would be imperative to sulfur transformation in anoxic environments (Stoffels et al, 2012). The presence of genes involved in both elemental sulfur and thiosulfate reduction suggests that these archaea may be key players in the reduction of intermediate sulfur species at the SMTZ redox layer.…”

Anorganski spojevi sumpora u ljudskom tijelu. I. Okso-spojevi.

“…61 Bakterije prisutne u lumenu debelog crijeva proizvode sulfide redukcijom sulfata i sulfita unesenih hranom, fermentacijom aminokiselina koje sadrže sumpor te metabolizmom mukopolisaharida koji u svojem sastavu imaju sulfate. 87 Sisavci se štite od toksičnih učinaka sulfida tako što ih u mitohondrijima stanica sluznice debelog crijeva oksidiraju u tiosulfat. Sulfidi se u mitohondrijima oksidiraju u tiosulfate složenim nizom enzimskih reakcija.…”

“…Stvorenim tiosulfatom crijevne bakterije se koriste namjesto kisikom za respiraciju. 87 Rodovi crijevnih bakterija koji ponajviše reduciraju tiosulfat su Salmonella, Proteus, Edwardsiella i Citrobacter.…”