Production of multiple bacteriocins, including the novel bacteriocin gassericin M, by Lactobacillus gasseri LM19, a strain isolated from human milk.

Bacteriocins are antimicrobial peptides produced by bacteria, and their production is regarded as a desirable probiotic trait. We found that Lactobacillus gasseri LM19, a strain isolated from human milk, produces several bacteriocins, including a novel bacteriocin, gassericin M. These bacteriocins were purified from culture and synthesised to investigate their activity and potential synergy. L. gasseri LM19 was tested in a complex environment mimicking human colon conditions; it not only survived, but expressed the seven bacteriocin genes and produced short-chain fatty acids. Metagenomic analysis of these in vitro colon cultures showed that co-inoculation of L. gasseri LM19 with Clostridium perfringens gave 16S ribosomal RNA metagenomic profiles with more similarity to controls than to vessels inoculated with C. perfringens alone. These results indicate that L. gasseri LM19 could be an interesting candidate for maintaining homeostasis in the gut environment.