Purification and molecular characterization of antibacterial compounds produced by Lactobacillus murinus strain L1

Abstract

Aims: The aim of this work was to purify and characterize antibacterial compounds produced by Lactobacillus murinus strain L1. Methods and Results: Antagonistic activity was observed in a deferred agar-spot assay against spoilage and pathogenic bacteria, but not against lactobacilli. The inhibitory activity occurred between pH 3AE0 and 5AE0, and was heat stable. The active compounds were purified by gel filtration chromatography and two peaks of antibacterial activity were observed using Bacillus cereus ATCC 11778 and Shigella sonnei ATCC 11060 as indicator strains. Two active low molecular weight compounds were responsible for this phenomenon and UV spectroscopy, gas chromatography and mass spectrometry were used to characterize them. One of them is lactic acid, while the other is a mono-substituted aromatic ring apparently constituted by group residues of m/z 192 linked in tandem to phenylalanine. Conclusions: Lactobacillus murinus produces at least two low molecular weight compounds active against B. cereus and Sh. sonnei. Significance and Impact of the Study: This is the first purification of a new broad-spectrum antibacterial compound from Lact. murinus which inhibits various pathogenic and food spoilage bacteria without acting on other lactobacilli. Using it as a biotechnological control agent of bacterial spoilage may be a promising possibility for the food industry.

Vaginal lactic acid bacteria in the mare: evaluation of the probiotic potential of native Lactobacillus spp. and Enterococcus spp. strains

“…Lactic and other organics acids are produced by LAB metabolism and are frequently associated with the microbial inhibition observed in vitro (Nardi et al 2005). As inhibition was neither abolished by proteolytic nor by thermal treatments, antibacterial activity might not be due to secreted microbial proteins.…”

Selective enrichment of commensal gut bacteria protects againstCitrobacter rodentium-induced colitis

“…L. murinus is one of eight bacterial species (collectively termed altered Schaedler's flora) used to restore cecal morphology of germ-free mice to a structure more comparable to specific pathogen-free mice (18). L. murinus produces a number of low-molecular-weight anti-microbial compounds (54). It has been reported to protect against Salmonella Typhimurium invasion of epithelial cells in vitro, and, when used in combination with other probiotic strains, L. murinus alleviates symptoms of S. Typhimurium infection and reduces pathogen shedding in infected pigs in vivo (7,8).…”

In vitro activity of potential probiotic Lactobacillus murinus isolated from the dog

“…murinus isolated from murine faeces have been characterized. One of these compounds is lactic acid, while the other is possibly a polymer of n heptose linked in tandem to phenylalanine moiety (Nardi et al. 2005).…”