Interaction between lactic acid bacteria and bile acids: Molecular and biophysical insights

Abstract

Dynamic interactions between microbes and host are essential to stimulate the immune system, maintain intestinalhomeostasis, and prevent pathogen colonization. In recent decades lactic acid bacteria (LAB) havereceived attention due to their probiotic potential and their impact on gut microbiota and host health. This paperaims to review the main molecular mechanisms by which bile acids (BA) modify the composition of the intestinalmicrobiota and bacterial viability, with special emphasis on the effect on LAB. The results discussed here suggestthat the BA disorganize the structure of the bacterial cell wall, modify their surface properties, their adhesioncapacity and compromise the integrity of the membranes, with loss of essential ions and nutrients. They thenenter the cell interior, at rates that depend on their hydrobicity. There, they dissociate, causing intracellularacidification and dissipation of membrane potential. This leads to a deficiency in the biological energy needed forcritical processes, leading to cell death at high concentrations. In addition, BA causes alteration and oxidation ofproteins and nucleic acids. The extent of damage caused by BA is influenced by their structure, physicochemicalproperties—particularly hydrophobicity—and concentration. The response of LAB depends on both theirintrinsic and adaptive mechanisms. Advancing research on these interactions represents a new frontier, enablingthe development of strategies to modulate intestinal microbiota composition, ultimately benefiting humanhealth.