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

Abstract

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 in vitro. Under anaerobic conditions, Escherichia coli ΔdsbB displayed reduced growth and decreased intracellular protein DSB levels, but polysulfide treatment restored both growth and DSB content. Similarly, polysulfide treatment of E. coli ΔdsbA promoted periplasmic roGFP2 DSB formation and recovered growth under anaerobic conditions. Furthermore, treating Schizosaccharomyces pombe and Cupriavidus pinatubonensis 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.