EHEC utilizes two-component systems to modulate expression of the major flagellar subunit protein, FliC, in response to host intestinal cues

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a food- and water-borne human enteric pathogen that infects human hosts. In order to colonize the host, EHEC uses many virulence factors including flagella to reach its site of colonization in the distal colon. Expression of flagella can be modulated in response to microenvironmental conditions within the host, sensed by two-component systems (TCS). We have demonstrated through immunoblot and motility assays that small intestinal short-chain fatty acid (SCFA) mixes upregulate flagella expression while large intestinal mixes downregulate expression in WT EHEC. We have also shown that three specific TCSs in EHEC are necessary for establishment of the SCFA-induced WT phenotype. Our results suggest that the ArcAB and RcsBC TCSs positively modulate flagella expression in response to small intestinal-like environmental conditions, while the BarA/UvrY TCS negatively modulates flagella expression in response to large intestinal-like environmental cues.