Sensing and regulation of reactive sulfur species (RSS) in bacteria

The infected host deploys generalized oxidative stress caused by small inorganic reactive molecules as antibacterial weapons. An emerging consensus is that hydrogen sulfide (H₂S) and forms of sulfur with sulfur-sulfur bonds termed reactive sulfur species (RSS) provide protection against oxidative stressors and antibiotics, as antioxidants. Here, we review our current understanding of RSS chemistry and its impact on bacterial physiology. We start by describing the basic chemistry of these reactive species and the experimental approaches developed to detect them in cells. We highlight the role of thiol persulfides in H₂S-signaling and discuss three structural classes of ubiquitous RSS sensors that tightly regulate cellular H₂S/RSS levels in bacteria, with a specific focus on the chemical specificity of these sensors.