Modulation of gut microbiota by Lactobacillus rhamnosus GG (LGG modulation of gut microbiota)

The concept "gut microbiota modulation by Lactobacillus rhamnosus GG" does not represent a *single molecular target* such as a receptor, enzyme, or transporter. Instead, it refers to the *collection of molecular mechanisms* through which the probiotic bacterium **Lactobacillus rhamnosus GG (LGG)** exerts beneficial effects on the host by altering the composition and function of the intestinal microbiota. LGG promotes health through multiple modes: - **Colonization and competitive exclusion:** LGG uses specialized pili to adhere strongly to the intestinal epithelium, thereby outcompeting pathogenic bacteria for binding sites and reducing their colonization[1][8]. - **Secretion of bioactive effector molecules:** LGG produces antimicrobial substances such as bacteriocins and organic acids (like lactic acid) that inhibit the growth of pathogens. It also secretes proteins (e.g., HM0539) and extracellular vesicles that enhance epithelial barrier function and immunomodulatory responses[3][4]. - **Enhancement of barrier integrity:** LGG stimulates host cell survival, maintains tight junctions, and induces mucin production, which strengthen the gut barrier and protect against injury and inflammation[4]. - **Immunomodulation:** By reducing production of pro-inflammatory cytokines, enhancing IgA secretion, and modifying immune signaling (e.g., via TLR4/MyD88/NF-κB pathways), LGG supports immune tolerance and homeostasis[4]. - **Metabolic effects:** LGG interacts with host signaling systems (e.g., FXR–FGF-15 axis) to affect bile acid metabolism, which, in animal models, can reduce liver injury and fibrosis[6]. It also regulates bone mass and metabolic inflammation in experimental systems[5][7]. Overall, *modulation of the gut microbiota by Lactobacillus rhamnosus GG* is not a discrete therapeutic target but a summary of the multifaceted, interlinked biological effects mediated by a living probiotic organism. Accordingly, there is something incorrect with considering it as a singular target for drug discovery: it is a mechanism of action/higher-level functional outcome, not a molecular entity (protein, receptor, etc.) amenable to direct pharmacological targeting.

Other names

Lactobacillus rhamnosus GG-mediated microbiota modulationLGG-modulated gut microbiome

Inhibition of pathogen colonization via competitive adhesion to intestinal mucosa - Secretion of effector molecules (e.g., pili, secreted proteins, bacteriocins, lactic acid) that modulate the intestinal environment and inhibit pathogens - Enhancement of mucosal barrier integrity (e.g., via stimulation of mucin and tight junction protein expression) - Immune modulation (e.g., reduced pro-inflammatory signaling, enhanced IgA secretion) - Modulation of host metabolic and signaling pathways (e.g., FXR–FGF-15, bone metabolism)[1][3][4][6]