Transcriptional autoregulation of the RcsCDB phosphorelay system in Salmonella enterica serovar Typhimurium

Abstract

The RcsCDB (Rcs) phosphorelay system is involved in the regulation of many envelope genes, such as those responsible for capsule synthesis, flagella production and O-antigen chain length, as well as in other cellular activities of several enteric bacteria. The system is composed of three proteins: the sensor RcsC, the response regulator RcsB, and the phospho-transfer intermediary protein RcsD. Previously, we reported two important aspects of this system: (a)rcsBgene expression is under the control of PrcsDBand PrcsBpromoters, and (b)rcsDgene transcription decreases when the bacteria reach high levels of the RcsB regulator. In the present work, we demonstrate that the RcsB protein repressesrcsDgene expression by binding directly to the PrcsDBpromoter, negatively autoregulating the Rcs system. Furthermore, we report the physiological role of the RcsB regulator, which is able to modify bacterial swarming behaviour when expressed under the control of the PrcsBpromoter.