Control of Escherichia coli O157:H7 Motility and Biofilm Formation by Salicylate and Decanoate: MarA/SoxS/Rob and pchE Interactions.

Prophage-encoded Escherichia coli O157:H7 transcription factor (TF), PchE, inhibits biofilm formation and attachment to cultured epithelial cells by reducing curli fimbriae expression and increasing flagella expression. To identify pchE regulators that might be used in intervention strategies to reduce environmental persistence or host infections, we performed a computational search of O157:H7 strain PA20 pchE promoter sequences for binding sites used by known TFs. A common site shared by MarA/SoxS/Rob TFs was identified and the typical MarA/Rob inducers, salicylate and decanoate, were tested for biofilm and motility effects. Sodium salicylate, a proven biofilm inhibitor, but not sodium decanoate, strongly reduced O157:H7 biofilms by a pchE-independent mechanism. Both salicylate and decanoate enhanced O157:H7 motility dependent on pchE using media and incubation temperatures optimum for culturing human epithelial cells. However, induction of pchE by salicylate did not activate the SOS response. MarA/SoxS/Rob inducers provide new potential agents for controlling O157:H7 interactions with the host and its persistence in the environment. IMPORTANCE There is a need to develop E. coli serotype O157:H7 non-antibiotic interventions that do not precipitate the release and activation of virulence factor-encoded prophage and transferrable genetic elements. One method is to stimulate existing regulatory pathways that repress bacterial persistence and virulence genes. Here we show that certain inducers of MarA and Rob have that ability, working through both pchE-dependent and -independent pathways.