Among the best characterized bacteriocins are those produced by Escherichia coli, which are known as colicins. The majority of 20s Proteasome activity colicins act by membrane permeabilization, followed by nuclease activity, while one colicin, colicin M, inhibits peptidoglycan synthesis. Uptake of colicin M proceeds by binding to the FhuA

outer membrane receptor followed by energy-dependent translocation into the periplasm through the TonB system (TonB, ExbB and ExbD) and the click here proton motive force of the inner membrane [3]. Colicin M is a phosphotase that cleaves the undecaprenyl-phosphate-linked peptidoglycan precursor, lipid II producing free undecaprenol and 1-pyrophospho-Mur-GlCNAc-pentapeptide. In the periplasm, hydrolysis of peptidoglycan lipid precursors results in arrest of polymerization steps and cell lysis [4]. Operons that encode colicin M and B are tightly linked on large conjugative plasmids [5, 6], and these are among the most abundant colicins produced by E. coli strains [7]. A number of studies have been aimed at defining the function of colicins in microbial communities. They might serve to enable invasion or defense of an ecological niche [8]. They have been shown to mediate population and community level interactions, promoting microbial diversity

within E. coli populations in the mammalian colon [9]. To obtain more insight into the ecological roles of one of the most prevalent Adavosertib supplier colicins, the effects of subinhibitory concentrations of colicin M on genome wide transcription in E. coli was studied. Antibiotic resistance currently represents one of the greatest worldwide threats to human health therefore, novel antibiotics are urgently needed. Antibiotic resistance among the Enterobacteriaceae represents a particular threat [10, 11]. As colicin M promotes the irreversible hydrolysis of lipid new II, a peptidoglycan lipid intermediate that is common to all bacteria, it is also a promising candidate for development

of a novel antimicrobial agent [12]. Analysis of the gene expression profile was thus also undertaken, to acquire insight into adaptive responses to colicin M that might be detrimental during antimicrobial therapy. Results and discussion Transcriptome analysis of E. coli MG1655 exposed to subinhibitory concentrations of colicin M The effects of colicin M on whole genome transcription of E. coli MG1655, a laboratory strain with minimal genetic manipulation that approximates the wild type [13], was investigated by microarray analysis. To choose the appropriate conditions for determing the colicin M induced transcriptome, mid-exponential phase cultures of strain MG1665 were exposed to various concentrations of colicin M and the growth response was monitored. On the basis of these results a concentration of 30 ng/ml was determined as subinhibitory and chosen for transcriptome analysis.