Abstract
Elemental sulfur and sulfite have been used to inhibit the growth of yeasts, but thiosulfate has not been reported to be toxic to yeasts. We observed that thiosulfate was more inhibitory than sulfite to Saccharomyces cerevisiae growing in a common yeast medium. At pH < 4, thiosulfate was a source of elemental sulfur and sulfurous acid, and both were highly toxic to the yeast. At pH 6, thiosulfate directly inhibited the electron transport chain in yeast mitochondria, leading to reductions in oxygen consumption, mitochondrial membrane potential and cellular ATP. Although thiosulfate was converted to sulfite and H2S by the mitochondrial rhodanese Rdl1, its toxicity was not due to H2S as the rdl1-deletion mutant that produced significantly less H2S was more sensitive to thiosulfate than the wild type. Evidence suggests that thiosulfate inhibits cytochrome c oxidase of the electron transport chain in yeast mitochondria. Thus, thiosulfate is a potential agent against yeasts.
Highlights
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; School of Molecular Biosciences, Washington State University, Pullman, WA 991647520, USA
Thiosulfate is spontaneously produced by reacting sulfite with elemental sulfur [1], and it is a key intermediate in the biogeochemical cycle of sulfur [2]
(C) The thiosulfate or sulfite tolerance assay on SD agar plates
Summary
Thiosulfate is spontaneously produced by reacting sulfite with elemental sulfur [1], and it is a key intermediate in the biogeochemical cycle of sulfur [2]. Yeast uses sulfate transporters to uptake thiosulfate and uses a mitochondrial rhodanese Rdl to transfer a zero-valence sulfur from thiosulfate to glutathione (GSH), producing glutathione persulfide (GSSH). Elemental sulfur (S0 ) [15] Both sulfite and S0 are toxic to yeast. Antioxidants 2021, 10, 646 spontaneously reacts with RSn H to produce H2 S and GSSG, and S0 toxicity could be due to the combination of thiol modification and H2 S production [32]. We report that thiosulfate is more inhibitory than sulfite to the yeast. At low pH, thiosulfate is converted to S0 and H2 SO3 , both of which are toxic; at neutral pH, thiosulfate is inhibitory by itself
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