OxyR senses reactive sulfane sulfur and activates genes for its removal in Escherichia coli

Reactive sulfane sulfur species such as hydrogen polysulfide and organic persulfide are newly recognized as normal cellular components, involved in signaling and protecting cells from oxidative stress. Their production is extensively studied, but their removal is less characterized. Herein, we showed that reactive sulfane sulfur is toxic at high levels, and it is mainly removed via reduction by thioredoxin and glutaredoxin with the release of H2S in Escherichia coli. OxyR is best known to respond to H2O2, and it also played an important role in responding to reactive sulfane sulfur under both aerobic and anaerobic conditions. It was modified by hydrogen polysulfide to OxyR C199-SSH, which activated the expression of thioredoxin 2 and glutaredoxin 1. This is a new type of OxyR modification. Bioinformatics analysis showed that OxyRs are widely present in bacteria, including strict anaerobic bacteria. Thus, the OxyR sensing of reactive sulfane sulfur may represent a conserved mechanism for bacteria to deal with sulfane sulfur stress.