Understanding strain dynamics of E. coli in the GI tract may provide a more sound approach to both probiotic strain choice and methods of administration [5–8]. One powerful predictor of the ability of a strain of INCB28060 cell line E. coli to competitively exclude or displace other strains is the production of one or more

of a large family of narrow spectrum antimicrobials, the bacteriocins. Theoretical studies have shown that bacteriocin production enhances the invasion and establishment success of the producing strains [9, 10]. In vivo studies further demonstrate that bacteriocin production improves the establishment success of its producing strain [11]. Similar results were obtained when mice harboring bacteriocin-sensitive strains were co-caged with mice harboring bacteriocin-producing strains. Within a relatively short period (three to five weeks) the

sensitive strains had been displaced by the bacteriocin-producing strains [12]. E. coli are prolific producers of their own species-specific bacteriocins, known as colicins, which were first identified over 80 years ago [13], and given the name colicin to identify the producing species. The frequency of colicin production varies among E. coli populations depending on the host species check details diet [14], the relatedness of the E. coli strains present [15], and the habitat quality [16]. However, on average, forty percent of the strains in any population are likely to produce one or more colicins [17, 18]. Over thirty colicins have been characterized to date, all of which are plasmid-encoded, high molecular oxyclozanide weight proteins that are induced in times of stress [19]. Upon release of colicins from the producing cell, the toxins kill their targets primarily by membrane permeabilization or nucleic acid degradation [20]. Genes encoding colicin functions are found in clusters that include a toxin-encoding

gene; an immunity gene, encoding a protein conferring self-specific protection to the cell against its own colicin; and, frequently, a lysis gene, encoding a protein involved in colicin release via lysis or pseudo-lysis of the producing cell [19]. It has recently been suggested that bacteriocin production is a critical factor in determining the establishment success of probiotic bacteria in humans and animals [21]. To investigate this hypothesis, we introduced E. coli strains differing only in the carriage and identity of bacteriocin-encoding GF120918 chemical structure plasmids into the GI tract of mice. The importance of bacteriocin production in colonization and persistence of their E. coli hosts in the mouse intestine was elucidated over time providing a rare and novel glimpse into the impact of bacteriocins on the establishment of enteric bacteria in the mouse GI tract. Results This study was designed to examine the colonization and persistence of colicinogenic E. coli strains in the mouse GI tract following a single administration.