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The Heterotrophic Bacterium Cupriavidus pinatubonensis JMP134 Oxidizes Sulfide to Sulfate with Thiosulfate as a Key Intermediate.

ABSTRACT: Heterotrophic bacteria actively participate in the biogeochemical cycle of sulfur on Earth. The heterotrophic bacterium Cupriavidus pinatubonensis JMP134 contains several enzymes involved in sulfur oxidation, but how these enzymes work together to oxidize sulfide in the bacterium has not been studied. Using gene-deletion and whole-cell assays, we determined that the bacterium uses sulfide:quinone oxidoreductase to oxidize sulfide to polysulfide, which is further oxidized to sulfite by persulfide dioxygenase. Sulfite spontaneously reacts with polysulfide to produce thiosulfate. The sulfur-oxidizing (Sox) system oxidizes thiosulfate to sulfate. Flavocytochrome c sulfide dehydrogenase enhances thiosulfate oxidation by the Sox system but couples with the Sox system for sulfide oxidation to sulfate in the absence of sulfide:quinone oxidoreductase. Thus, C. pinatubonensis JMP134 contains a main pathway and a contingent pathway for sulfide oxidation.IMPORTANCE We establish a new pathway of sulfide oxidation with thiosulfate as a key intermediate in Cupriavidus pinatubonensis JMP134. The bacterium mainly oxidizes sulfide by using sulfide:quinone oxidoreductase, persulfide dioxygenase, and the Sox system with thiosulfate as a key intermediate. Although the purified and reconstituted Sox system oxidizes sulfide, its rate of sulfide oxidation in C. pinatubonensis JMP134 is too low to be physiologically relevant. The findings reveal how these sulfur-oxidizing enzymes participate in sulfide oxidation in a single bacterium.

SUBMITTER: Xin Y

PROVIDER: S-EPMC7642071 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Heterotrophic bacteria have recently been reported to oxidize sulfide to sulfite and thiosulfate by using sulfide:quinone oxidoreductase (SQR) and persulfide dioxygenase (PDO). In chemolithotrophic bacteria, both SQR and PDO have been reported to function in the periplasmic space, with SQR as a peripheral membrane protein whose C terminus inserts into the cytoplasmic membrane and PDO as a soluble protein. Cupriavidus pinatubonensis JMP134, best known for its ability to degrade 2,4-dichlorophenoxyacetic acid and other aromatic pollutants, has a gene cluster of sqr and pdo encoding C. pinatubonensis SQR (CpSQR) and CpPDO2. When cloned in Escherichia coli, the enzymes are functional. Here we investigated whether they function in the periplasmic space or in the cytoplasm in heterotrophic bacteria. By using sequence analysis, biochemical detection, and green fluorescent protein (GFP)/PhoA fusion proteins, we found that CpSQR was located on the cytoplasmic side of the membrane and CpPDO2 was a soluble protein in the cytoplasm with a tendency to be peripherally located near the membrane. The location proximity of these proteins near the membrane in the cytoplasm may facilitate sulfide oxidation in heterotrophic bacteria. The information may guide the use of heterotrophic bacteria in bioremediation of organic pollutants as well as H2S.IMPORTANCE Sulfide (H2S, HS-, and S2-), which is common in natural gas and wastewater, causes a serious malodor at low levels and is deadly at high levels. Microbial oxidation of sulfide is a valid bioremediation method, in which chemolithotrophic bacteria that use sulfide as the energy source are often used to remove sulfide. Heterotrophic bacteria with SQR and PDO have recently been reported to oxidize sulfide to sulfite and thiosulfate. Cupriavidus pinatubonensis JMP134 has been extensively characterized for its ability to degrade organic pollutants, and it also contains SQR and PDO. This paper shows the localization of SQR and PDO inside the cytoplasm in the vicinity of the membrane. The information may provide guidance for using heterotrophic bacteria in sulfide bioremediation.

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The Heterotrophic Bacterium Cupriavidus pinatubonensis JMP134 Oxidizes Sulfide to Sulfate with Thiosulfate as a Key Intermediate.

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