Probiotic Bacteria Deliver Novel Glucose-Dependent Broad Spectrum Effectors In Membrane Vesicles.

Lactobacillus rhamnosus GG is a Gram-positive beneficial bacterium that resides in the human intestinal tract and as probiotics provide numerous benefits for human health. We found that Lactobacillus rhamnosus GG eliminates the pathogens Enterococcus faecalis and Salmonella typhimurium during fermentation. We purified and identified acid-stable protein effector that contributes to this antagonistic activity. This protein, HtrA serine peptidase, changes its conformation and exerts membrane damage during glucose fermentation. Genomic analysis revealed that it is conserved within the lactobacilli clade. Interestingly, although this effector protein lacks a signal peptide for secretion, it is delivered to the recipient cells by membrane vesicles. Collectively, our results provide an appealing explanation of the effects of nutrition on the elimination of pathogens by the probiotic bacteria.