Expression of attaching/effacing activity by enteropathogenic Escherichia coli depends on growth phase, temperature, and protein synthesis upon contact with epithelial cells.

Enteropathogenic Escherichia coli (EPEC) induces tyrosine phosphorylation of a 90-kDa protein (Hp90) in infected epithelial cells. This in turn facilitates intimate binding of EPEC via the outer membrane protein intimin, effacement of host cell microvilli, cytoskeletal rearrangement, and bacterial uptake. This phenotype has been commonly referred to as attaching/effacing (A/E). The ability of EPEC to induce A/E lesions was dependent on bacterial growth phase and temperature. Early-logarithmic-phase EPEC grown at 37 degrees C elicits strong A/E activity within minutes after infection of HeLa epithelial cells. EPEC de novo protein syntheses during the first minutes of interaction with the host cell was required to elicit A/E lesions. However, once formed, bacterial viability was not needed to maintain A/E lesions. The type of growth media and partial O2 pressure level do not seem to affect the ability of EPEC to cause A/E lesions. These results indicates that the A/E activity of EPEC is tightly regulated by environmental and host factors.