Bile resistance mechanisms in Lactobacillus and Bifidobacterium

Abstract

Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. Most of the probiotic bacteria currently available in the market belong to the genera Lactobacillus and Bifidobacterium, and specific health-promoting activities, such as treatment of diarrhea or amelioration of gastrointestinal discomfort, have been attributed to them. In order to be able to survive the gastrointestinal transit and transiently colonize our gut, these bacteria must be able to counteract the deleterious action of bile salts, which are the main components of bile. Bile salts are detergent-like biological substances synthesized in the liver from cholesterol. Host enzymes conjugate the newly synthesized free bile acids in the liver with the amino acids glycine or taurine, generating conjugated bile salts. These compounds are stored in the gall bladder and they are released into the duodenum during digestion to perform their physiological function, which is the solubilization of fat coming from diet. These bile salts possess strong antimicrobial activity, since they are able to disorganize the structure of the cell membrane, as well as trigger DNA damage. This means that bacteria inhabiting our intestinal tract must have intrinsic resistance mechanisms to cope with bile salts. To do that, Lactobacillus and Bifidobacterium display a variety of proteins devoted to the efflux of bile salts or protons, to modify sugar metabolism or to prevent protein misfolding. In this manuscript, we review and discuss specific bile resistance mechanisms, as well as the processes responsible for the adaptation of bifidobacteria and lactobacilli to bile.

Crystal Structure of the Substrate-Binding Domain from Listeria monocytogenes Bile-Resistance Determinant BilE

“…One of the major challenges to bacterial growth and survival in the gastrointestinal tract is the presence of bile (for reviews, including mechanisms of toxicity and bacterial resistance, see References [10][11][12][13]). Bile is a digestive secretion produced by the liver and stored and concentrated in the gallbladder before being released into the lower intestine, where it aids in the emulsification and solubilization of fats.…”

Bile acid–microbiota crosstalk in gastrointestinal inflammation and carcinogenesis: a role for bifidobacteria and lactobacilli?

“…In this Review, the authors identified possible therapeutic targets from data published in the context of gastrointestinal inflammation and carcinogenesis. From the microbial point of view, BAs are one of the main factors deter mining probiotic survival through the human gastrointestinal tract, which indeed was the focus of my PhD work 2 .…”

Bile salt hydrolase and antimicrobial activities of three bile resistant probiotics Lactobacillus plantarum strains isolated from Cameroonian artisanal fermented milk

“…The latter are excreted more rapidly from the intestinal tract than those which are conjugated. Thus, free bile acids are excreted from the body through feces and the synthesis of new bile salts from serum cholesterol as substrate leads to a reduction in the total concentration of cholesterol in the blood (27,28). Our results on the BSH activity showed that L. plantarum GGU, L. plantarum GLA51 and L. plantarum GLP56 exhibited BSH activity towards Oxgall and Taurodeoxycholate bile salts.…”