RcsB-dependent effects on nar operon regulation during the aerobic growth of Salmonella Typhimurium

The intracellular pathogen Salmonella is an important cause of human foodborne diseases worldwide. Salmonella takes advantage of the phosphorelay regulatory systems to survive in the hostile environment of the host's gastrointestinal tract. It has been reported that the nitrate reductase Z (NR-Z), encoded by the narUZYV operon, is required during Salmonella transition to anaerobic environments and is constitutively produced at low levels, but little is known about the regulatory mechanism involved in the operon gene expression. In this work, we found that the RcsCDB system is activated by high concentrations of specific sugars as a carbon source. In this activation state, the RcsCDB system participates in the negative control of narUZYWV expression. This control strategy occurs during exponential growth when the carbon source is high, allowing for normal aerobic respiration. The RcsCDB system's participation in aerobic respiration is necessary to ensure efficient metabolism and optimal energy consumption when the bacteria are growing exponentially.