Operon structure and gene expression of the espJ--tccP locus of enterohaemorrhagic Escherichia coli O157:H7.

In this study, we investigated the genetic organisation and expression of the espJ--tccP locus of enterohaemorrhagic Escherichia coli (EHEC O157:H7), which encodes the type III secretion system effector proteins EspJ and TccP. Using flow cytometry and fluorescence microscopy, we found that espJ and tccP constitute an operon, whose expression in vitro is affected by the composition of the medium and environmental signals such as temperature, pH, osmolarity and O(2) pressure. Moreover, expression of the espJ--tccP operon is not regulated by Ler, a LEE-encoded transcriptional regulator, but by an as yet unidentified regulatory system(s).