Among the various peptides, lipopeptides are well known to inhibit the growth of fungi and bacteria including opportunistic pathogens. Consequently, naturally produced antimicrobial lipopeptides have been receiving increased attention due to their anti-infective nature with wide antimicrobial spectrum. Besides the activity of natural peptides, any chemical modifications in structure of these lipopeptide are shown to improve their spectrum and activity. To this effect, daptomycin, an anionic lipopeptide has already been used for therapeutic applications [26]. While antimicrobial lipopeptides are produced by different Gram-positive and Gram-negative bacteria,

only lipopeptides produced by species of Pseudomonas and Bacillus have been studied in detail [13, 14, Selleck NU7026 27–29]. In the present study several antimicrobial substances producing bacterial strains were isolated from a fecal contaminated soil sample and characterization of these substances revealed them as antimicrobial lipopeptides. The phenotypic features like Gram-negative staining, catalase positive, oxidase negative, facultative anaerobic growth and citrate utilization observed for all strains learn more suggested that they belong to the Enterobacteriaceae family, usually observed in fecal matter. The 16S rRNA gene sequence blast analysis and subsequent

phylogentic analysis assigned all strains to different species of the genera Citrobacter and Enterobacter. Interestingly, though strains S-5 and S-9 displayed high identity with E. hormaechei and E. mori respectively in 16S rRNA gene sequence, they only formed an out group to the cluster comprised of different Enterobacter and Citrobacter species (Figure 2). However, the overall topology of neighbour-joining tree revealed the phylogenetic complexity and discrepancies

in 16S rRNA gene sequences of strains Luminespib in vitro belonging to the family Enterobacteriaceae. It was also supported by the unusual inclusion of different species belonging to Unoprostone genera Citrobacter and Enterobacter in the same cluster suggesting the need to revisit the family Enterobacteriaceae. The antimicrobial lipopeptides typically contain a cyclic or linear oligopeptide linked with a β-hydroxy fatty acid tail of varied lengths [28]. Inhibition spectra of these lipopeptides are influenced by the composition of oligopeptide as well as fatty acid component [30, 31]. Antimicrobial lipopeptides are largely produced by Gram-positive bacteria like Bacillus sp. and are classified into different families based on the composition of oligopeptides and antibacterial or antifungal activities [32]. Among the Gram-negative bacteria, Pseudomonas is the only genus reported to produce antimicrobial lipopeptides such as massetolide, viscosin [33], syringomycin [34], arthrofactin [35], pseudodesmins [36], orfamide [16] and putisolvin [37]. In addition to these lipopeptides, species like P. fluorescens was reported to produce different massetolide analogues [33].