Molecular analysis of biofilm formation by Enteropathogenic Escherichia coli (EPEC) O119

Abstract

EPEC can be categorized into two subgroups, typical (tEPEC) and atypical (aEPEC), based on the presence or absence of the EPEC adherence factor plasmid (pEAF), respectively. EPEC colonizes the proximal small intestine, where it adheres to epithelial cells forming microcolonies. Microcolony formation is one of the initial steps in biofilm development, but, very little is known regarding biofilm formation by EPEC strains. Our laboratory investigated the ability of biofilm formation in a collection of 223 EPEC strains (70 typical and 153 atypical) belonged to EPEC and non-EPEC serogroups. Among the biofilm-producing strains, two O119 strains (T29 and A111) formed a substantially robust biofilm and a dense pellicle at the air-liquid interface, and when grown on Congo red agar produced red, dry, aggregative colonies similar to the RDAR morphotype. Initial transposon mutagenesis analysis identified eight A111 mutants deficient in biofilm formation, pellicle at the air-liquid interface, and RDAR morphotype. DNA sequence analysis for the mutants displayed similarities to the type 1 fimbriae. The aims of this project are to (i) investigate the role of type I fimbriae in the initial stages of biofilm development and the involvement of YdeH in the regulation of genes expressed during biofilm formation by A111 strain, and (ii) identify the gene(s) involved in the formation of biofilm by T29 strain. (AU)