Bile Acid Stress in Lactic Acid Bacteria and Bifidobacteria
Abelardo Margolles and Atsushi Yokota
from: Lactic Acid Bacteria and Bifidobacteria: Current Progress in Advanced Research (Edited by: Kenji Sonomoto and Atsushi Yokota). Caister Academic Press, U.K. (2011)
Bile is mainly composed of bile acids, detergent-like biological substances synthesized from cholesterol in the liver. They are involved in the generation of bile flow, and their major physiological function is to facilitate the absorption of lipophilic compounds from the diet, including vitamins and lipids. Furthermore, bile also plays a crucial role in the establishment of the intestinal microbiota in humans, since bile salts are potent antimicrobial agents and only microbial populations able to cope with physiological concentrations of bile are able to survive in the gut. Bile disturbs the cell membrane functionality in lactic acid bacteria (LAB) and bifidobacteria due to its amphipatic property. Studies on the bile stress response in LAB and bifidobacteria revealed that bile resistance is a result of integration of multi-lateral responses, which include those that protect cell membrane from direct attack by bile acids, those that restore or degrade damaged proteins, those that eliminate oxidative stress and facilitate DNA repair, and those that enhance energy generation through up-regulated sugar metabolism. This chapter summarizes the current knowledge of the molecular mechanisms used by LAB and bifidobacteria to tolerate the deleterious action of bile salts read more ...