Progress on the function and regulatory mechanisms of bacterial Cpx signal transduction system

The Cpx (conjugative pilus expression) two-component signal transduction system is a complex envelope stress response system in Gram-negative bacteria, which can sense a variety of extracellular stimuli that enter the signaling pathway at different points. The phosphorylation of the CpxR, the cytoplasmic cognate response regulator of the Cpx system, can lead to changes in the expression of genes encoding proteins involved in inner and outer membrane functions. Activation of the Cpx system contributes to bacterial resistance/tolerance to certain antibiotics and acidic stress. In this review, we summarize the composition, and the mechanisms of signal detection, and the transcriptional regulation of the Cpx system, with a goal to provide guidance for the study of the regulatory network of the Cpx system and its important regulatory roles in bacterial physiology.