Environmental polysulfides promote protein disulfide bond formation of microorganisms growing under anaerobic condition

ABSTRACT Polysulfides are rich in anaerobic and microbial metabolism active environments. Anaerobic survival of microorganisms requires the formation of protein disulfide bond (DSB). The relation between environmental polysulfides and anaerobic DSB formation has not been studied so far. Herein, we discovered that environmental polysulfides can efficiently mediate protein DSB formation of microorganisms under anaerobic condition. We used polysulfides to treat proteins including roGFP2, Trx1, and DsbA under anaerobic condition and found that all three proteins formed intramolecular DSB in vitro . The growth of E. coli Δ dsbB was reduced and the amount of its intracellular protein DSB was decreased under anaerobic condition. However, treating the mutant strain with polysulfides recovered the growth and reversed DSB decrease. Treating E. coli Δ dsbA with polysulfides promoted DSB formation of its periplasmic roGFP2 and recovered its growth under anaerobic condition. In addition, treating Schizosaccharomyces pombe with polysulfides led to increase of the intracellular protein DSB content. Thus, our study reveals that environmental polysulfides can promote DSB formation independent of the enzymatic DSB mediating system and oxygen. In this aspect, environmental polysulfides are beneficial for the survival of microorganisms in anaerobic habitats. IMPORTANCE How polysulfides benefit adaption of microorganisms to anaerobic environments are unclear. Our study reveals that environmental polysulfides efficiently facilitate protein DSB formation under anaerobic condition. Polysulfides contain zero valent sulfur atoms (S 0 ), which can be transferred to the thiol group of cysteine residue. This S 0 atom gets two electrons from two cysteine residues and becomes reduced H 2 S, leaving two cysteine residues in disulfide bond form. Anaerobic growth of microorganisms was benefited from the formation of DSB. This finding paves the way for a deeper understanding of the intricate relationship between polysulfides and microorganisms in environmental contexts.