Fermentation regulates cell wall biosynthesis, biofilm formation and antimicrobial production in Lacticaseibacillus rhamnosus GG

Lacticaseibacillus rhamnosus GG is a Gram-positive beneficial bacterium that resides in the human intestinal tract and belongs to the family of lactic acid bacteria (LAB). This bacterium is a widely used probiotic species and was suggested to provide numerous benefits for human health. However, as in most LAB strains, the molecular mechanisms that mediate the competitiveness of probiotics under different diets remain unknown. Fermentation is a fundamental process in LAB, allowing the oxidation of simple carbohydrates (e.g., glucose, mannose) for energy production under conditions of oxygen limitation, as in the human gut. Our results indicate that fermentation reshapes the metabolome, volatilome, and proteome architecture in Lacticaseibacillus rhamnosus GG. Specifically, fermentation alters cell envelope and peptidoglycan biosynthesis, affecting cell wall thickness, aggregation properties, and cell wall composition. In addition, fermentation-induced secretion of known and novel bacteriocins and metabolites can target the pathogens Enterococcus faecalis and Salmonella typhimurium that share the same niche, the GI tract. At the same time, the secreted antimicrobials further enhance the cell wall remodeling of their own Lacticaseibacillus rhamnosus GG producers. Overall, our results link the common metabolic regulation of cell wall remodeling, aggregation to host tissues, biofilm formation in probiotic strains, and connect the production of antimicrobial effectors with metabolome reprogramming. Overall, these findings provide novel insights into nutrition`s role in Lacticaseibacillus rhamnosus GG establishment in the GI.