Polysulfides promote protein disulfide bond formation in microorganisms growing under anaerobic conditions

Polysulfides commonly occur in anaerobic, microbial active environments, where they play key roles in sulfur cycling and redox transformations. Anaerobic survival of microorganisms requires the formation of protein disulfide bond (DSB). The relationship between polysulfides and anaerobic DSB formation has not been studied so far. Herein, we discovered that polysulfides can efficiently mediate protein DSB formation of microorganisms under anaerobic conditions. We used polysulfides to treat proteins, including roGFP2, Trx1, and DsbA, under anaerobic conditions and found that all three proteins formed intramolecular DSB <i>in vitro</i>. Under anaerobic conditions, <i>Escherichia coli</i> Δ<i>dsbB</i> displayed reduced growth and decreased intracellular protein DSB levels, but polysulfide treatment restored both growth and DSB content. Similarly, polysulfide treatment of <i>E. coli</i> Δ<i>dsbA</i> promoted periplasmic roGFP2 DSB formation and recovered growth under anaerobic conditions. Furthermore, treating <i>Schizosaccharomyces pombe</i> and <i>Cupriavidus pinatubonensis</i> JMP134 with polysulfides increased their intracellular protein DSB content. Collectively, these findings demonstrate that polysulfides can promote DSB formation independently of known enzymatic DSB-mediated systems and the presence of oxygen, thereby benefiting the survival of microorganisms in anaerobic habitats.IMPORTANCEHow polysulfides enhance the adaption of microorganisms to anaerobic environments remains unclear. Our study reveals that polysulfides efficiently facilitate protein DSB formation under anaerobic conditions. Polysulfides contain zero-valent sulfur atoms (S⁰), which can be transferred to the thiol group of cysteine residue. This S⁰ atom then accepts two electrons from two cysteine residues and is reduced to H₂S, leaving the two cysteines linked by a disulfide bond. Anaerobic growth of microorganisms benefits from the formation of DSB. These findings pave the way for a deeper understanding of the intricate relationship between polysulfides and microorganisms in various environmental contexts.