Conditional Function of Autoaggregative Protein Cah and Common cah Mutations in Shiga Toxin-Producing Escherichia coli.

We examined the function of Cah in biofilm formation and host colonization to better understand selective pressures for cah mutations. EDL933-Cah played a conditional role in biofilm formation in vitro: it enhanced E. coli DH5α biofilm formation on glass surfaces under agitated culture conditions that prevented autoaggregation, but inhibited biofilm formation under hydrostatic conditions that facilitated autoaggregation. This function appeared to be strain-dependent since Cah-mediated biofilm formation was diminished when an EDL933-cah was expressed in SS17. Deletion of cah in EDL933 enhanced bacterial attachment to spinach leaves and altered the adherence pattern of EDL933 to bovine recto-anal junction squamous epithelial (RSE) cells. In contrast, in trans-expression of EDL933-cah in SS17 increased its attachment to leaf surfaces, and in DH5α, enhanced its adherence to RSE cells. Hence the ecological function of Cah appears to be modulated by environmental conditions and other bacterial strain-specific properties. Considering the prevalence of cah in STEC and its role in attachment and biofilm formation, cah mutations might be selected in ecological niches where inactivation of Cah would result in an increased fitness in STEC during colonization of plants or animal hosts.ImportanceShiga toxin-producing Escherichia coli (STEC) harbors genes encoding diverse adhesins and many of these are known to play an important role in bacterial attachment and host colonization. We demon...

Source: Applied and Environmental Microbiology - October 20, 2017 Category: Microbiology Authors: Carter MQ, Brandl MT, Kudva IT, Katani R, Moreau MR, Kapur V Tags: Appl Environ Microbiol Source Type: research