The Intimin-Like Protein FdeC Is Regulated by H-NS and Temperature in Enterohemorrhagic Escherichia coli

Donna M. Easton, Luke P. Allsopp, Minh-Duy Phan, Danilo Gomes Moriel, Guan Kai Goh, Scott A. Beatson, Timothy J. Mahony, Rowland N. Cobbold, Mark A. Schembri

Enterohaemorrhagic Escherichia coli (EHEC) are Shiga toxigenic pathogens capable of inducing severe forms of enteritis (e.g. hemorrhagic colitis) and extraintestinal sequelae (e.g. hemolytic uremic syndrome). The molecular basis of colonization of human and animal hosts by EHEC is not yet completely understood and an improved understanding of EHEC mucosal adherence may lead to development of interventions that could disrupt host colonization. FdeC, also referred to by its IHE 3034 locus tag ECOK1_0290, is an intimin-like protein that was recently shown to contribute to kidney colonisation in a mouse urinary tract infection model. The expression of FdeC is tightly regulated in vitro, and FdeC shows promise as a vaccine candidate against extra-intestinal E. coli strains. In this study we characterised the prevalence, regulation and function of fdeC in EHEC. We showed that the fdeC gene is conserved in both O157 and non-O157 EHEC, and encodes a protein that is expressed at the cell surface and promotes biofilm formation under continuous flow conditions in a recombinant E. coli strain background. We also identified culture conditions where FdeC is expressed, and showed that minor alterations of these conditions, such as changes in temperature, can significantly alter the level of FdeC expression. Additionally, we demonstrate that the transcription of the fdeC gene is repressed by the global regulator H-NS. Taken together, our data suggest a role for FdeC in EHEC when growing at temperatures above 37°C, a condition relevant to its specialized niche at the recto-anal junction of cattle.