Abstract
Members of the phylum Campylobacterota, which dominate deep-sea hydrothermal vent ecosystems, typically harbor the ability for thiosulfate oxidation through a complete sulfur oxidation (Sox) system encoded by the soxABXY 1 Z 1 and soxCDY 2 Z 2 gene clusters. Bioinformatic analysis identified a two-component regulatory system (TCS) SulRS in Sulfurimonas hydrogeniphila, a representative member of Campylobacterota. EMSA and DNase Ⅰ footprinting assays confirmed that SulR specifically binds to promoters Px, Py, and Pr, and its Px-binding sequence contains two conserved direct repeat sequences. Combined microscale thermophoresis (MST) and dual-plasmid reporter assays showed that SulS can senses thiosulfate signals and activates soxABXY 1 Z 1 transcription, whereas this substrate exerts no significant effect on soxCDY 2 Z 2 transcription. Genomic analysis further revealed that sulRS-soxABXY 1 Z 1 -like gene clusters are widely conserved among sulfur-oxidizing bacteria within Campylobacterota. These findings suggest that the SulRS may play a pivotal role in regulating sulfur oxidation, likely facilitating the response, adaptation, and survival of these bacteria in chemosynthetic environments rich in reduced sulfur compounds.