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“Background The endogenous human gut microbiome has several important functions including nourishment, the training of innate immunity and YM155 order the regulation of epithelial development [1]. Although the Escherichia coli population represents a rather small portion of the intestinal bacterial microflora, E. coli nonetheless occupy an important niche with regard to their close proximity to intestinal epithelium, wherein they utilize available oxygen and facilitate anaerobic growth [2]. Intestinal microflora also prevent the growth of pathogenic bacteria, either by competing for nutrient sources, or through direct bacterial antagonism mediated by bacteriocins and bacteriophages [3]. E. coli is a highly diverse species with respect to its gene content, phenotype and virulence [4]. Based on different virulence factors, E. coli strains can be classified

into three main groups: commensal, intestinal pathogenic and extraintestinal pathogenic E. coli (ExPEC) [5]. Commensal strains are commonly considered to be non-pathogenic. It has been shown that intestinal and extraintestinal pathogenic E. coli strains can develop from commensal strains by acquisition of virulence factors [6, 7]. Intestinal pathogenic (diarrhea-associated) E. coli is a typical mucosal pathogen which uses different Janus kinase (JAK) pathogenic strategies PRI-724 mouse including invasion of host cells (enteroinvasive E. coli, EIEC), production of enterotoxins (enterotoxigenic E. coli, ETEC) and production of Shiga-like toxins (enterohemorrhagic E. coli, EHEC) [8]. Enteropathogenic E. coli (EPEC) strains cause attaching-and-effacing (A/E) lesions and harbor the EAF plasmid [8]. Diffuse-adherent strains of E. coli (DAEC) are characterized by continuous adherence to eukaryotic cells mediated by afimbrial adhesins [9], while entero-aggregative (EAggEC) strains produce an aggregative adherence (AA) pattern [10] when

adhering to HEp-2 cells. ExPEC strains carry different combinations of virulence factors. Johnson et al. (2003) defined ExPEC strains as those possessing 2 or more of the following virulence factors: P fimbriae, S/F1C fimbriae subunits, Dr-antigen binding adhesins, aerobactin receptor and group 2 capsule synthesis [11]. Another important characteristic of human E. coli strains is production of bacteriocins. Colicins and microcins are antimicrobial agents with a relatively narrow spectrum of activity [12–14]. In general, microcins are known to have a wider spectra of antibacterial activity compared to colicins [14, 15]. Colicin Js [16, 17] is mTOR inhibitor unique in that it shares features of both colicins and microcins. The ecological role and molecular evolution of bacteriocinogeny are less clear but synthesis of bacteriocins may have both invasive and defensive functions in microbial communities [18].