Characterization of a Novel Promoter Region for the Enteropathogenic Escherichia coli Type III Secretion System Chaperone Gene cesT

Abstract

Enteropathogenic Escherichia coli (EPEC) is an enteric pathogen that causes potentially fatal infantile diarrhea. A type III secretion system is employed by EPEC to inject bacterial effector proteins directly into host intestinal epithelial cells. The multivalent chaperone, CesT, interacts with nine effectors and is a significant contributor to EPEC pathogenesis. A putative transcriptional promoter region was identified directly upstream of cesT. In silico analyses identified conserved elements that suggest the cesT promoter is recognized by ?70. Using transcriptional fusions to lux reporter genes I showed that the cesT promoter region is active under conditions known to induce virulence-gene expression. I conclude that the cesT promoter is active early during an in vitro assay, and regulated by different mechanisms than those affecting the Ptir operon promoter.