Recombinant Escherichia coli with sulfide:quinone oxidoreductase and persulfide dioxygenase rapidly oxidises sulfide to sulfite and thiosulfate via a new pathway

Abstract

Many heterotrophic bacteria contain sulfide:quinone oxidoreductase (SQR) and persulfide dioxygenase (PDO) genes. It is unclear how these enzymes cooperate to oxidise sulfide in bacteria. Cupriavidus pinatubonensis JMP134 contains a gene cluster of sqr and pdo, and their functions were analysed in Escherichia coli. Recombinant E. coli cells with SQR and PDO rapidly oxidised sulfide to thiosulfate and sulfite. The SQR also contains a DUF442 domain that was shown to have rhodanese activities. E. coli cells with PDO and SQR-C94S, an active site mutant of the rhodanese domain, oxidised sulfide to thiosulfate with transitory accumulation of polysulfides. Cellular and enzymatic evidence showed that DUF442 speeds up the reaction of polysulfides with glutathione to produce glutathione persulfide (GSSH). Thus, SQR oxidises sulfide to polysulfides; rhodanese enhances the reaction of polysulfides with glutathione to produce GSSH; PDO oxidises GSSH to sulfite; sulfite spontaneously reacts with polysulfides to generate thiosulfate. The pathway is different from the proposed mitochondrial pathway because it has polysulfides, that is, disulfide and trisulfide, as intermediates. The data demonstrated that heterotrophic bacteria with SQR and PDO can rapidly oxidise sulfide to thiosulfate and sulfite, providing the foundation for using heterotrophic bacteria with SQR and PDO for sulfide bioremediation.

Cytoplasmic Localization of Sulfide:Quinone Oxidoreductase and Persulfide Dioxygenase of Cupriavidus pinatubonensis JMP134

“…Since H 2 S is toxic at high levels (8), its concentration is usually maintained in a range, with excess H 2 S being metabolized in cells. A new sulfide oxidation pathway has been discovered from animal mitochondria (1,9), and the pathway is also present in heterotrophic bacteria (10)(11)(12). In bacteria, sulfide:quinone oxidoreductase (SQR) oxidizes sulfide to polysulfide, rhodanese speeds up the reaction of polysulfide with glutathione (GSH) to produce glutathione persulfide (GSSH), and persulfide dioxygenase (PDO) oxidizes GSSH to sulfite, which spontaneously reacts with polysulfide to produce thiosulfate (12).…”

“…SQR has been identified and studied in a variety of anaerobic phototrophic bacteria that use sulfide as the reducing power for photosynthesis and chemolithotrophic bacteria that oxidize sulfide to conserve energy for growth (14,15). Heterotrophic bacteria carrying SQR and PDO have been reported to oxidize sulfide (H 2 S, HS Ϫ , and S 2Ϫ ) to sulfite and thiosulfate (12), showing potential to be used in H 2 S bioremediation, which has been done with chemolithotrophic bacteria (16,17).…”

“…The periplasmic R. capsulatus SQR is a type I SQR (19). Type II SQRs were recently identified from animal mitochondria and bacteria, and they may play a detoxification role (4,12). Cupriavidus pinatubonensis (ex.…”

“…Cupriavidus pinatubonensis (ex. C. necator) JMP134 has been extensively studied for its ability to degrade a variety of organic pollutants, such as 2,4-dichlorophenoxyacetic acid and 2,4,6-trichlorophenol (31,32), and it contains an SQR (CpSQR) that is a fusion of a rhodanese domain and a type II SQR domain (12). The sqr gene is next to a pdo gene within the chromosome, coding for CpPDO2.…”

“…The sqr gene is next to a pdo gene within the chromosome, coding for CpPDO2. When both genes are expressed in Escherichia coli, the recombinant E. coli oxidizes sulfide to sulfite and thiosulfate (12). Further, C. pinatubonensis JMP134 contains another PDO, CpPDO1 (10).…”