Genetic Characterization of the Bile Salt Response in Lactobacillus plantarum and Analysis of Responsive Promoters In Vitro and In Situ in the Gastrointestinal Tract

Abstract

In this paper we describe the growth, morphological, and genetic responses of Lactobacillus plantarum WCFS1 to bile. Growth experiments revealed that a stepwise increase in the porcine bile concentration led to a gradual decrease in the maximal growth rate. Moreover, the final density reached by an L. plantarum culture growing in MRS containing 0.1% bile was approximately threefold lower than that in MRS lacking bile. The morphology of the cells grown in MRS containing 0.1% bile was investigated by scanning electron microscopy, which revealed that cells clumped together and had rough surfaces and that some of the cells had a shrunken and empty appearance, which clearly contrasted with the characteristic rod-shaped, smooth-surface morphology of L. plantarum cells grown in MRS without bile. An alr complementation-based genome-wide promoter screening analysis was performed with L. plantarum, which led to identification of 31 genes whose expression was potentially induced by 0.1% porcine bile. Remarkably, 11 membrane-and cell wall-associated functions appeared to be induced by bile, as were five functions involved in redox reactions and five regulatory factors. Moreover, the lp_0237 and lp_0775 genes, identified here as genes that are inducible by bile in vitro, were previously identified in our laboratory as important for L. plantarum in vivo during passage in the mouse gastrointestinal tract (

Bacteroides: the Good, the Bad, and the Nitty-Gritty

“…In turn, these organisms must be able to survive when exposed to the high concentration of bile salts in the intestinal tract. The detergent activity of bile salts permeabilizes bacterial membranes and can eventually lead to membrane collapse and cell damage (16,34,70). Factors that enable Bacteroides species to tolerate bile salts are important elements in their ability to survive in the gut.…”

Gut and Root Microbiota Commonalities

“…Different bile substances have been identified to control gene expression in bifidobacteria (129). Other bile-inducible genes have been found in Lactobacillus plantarum (130). Lastly, human gut bacteria transform bile salts (131).…”

Pathophysiology of increased intestinal permeability in obstructive jaundice

“…Absence of bile salts results in a disturbed intestinal bacterial balance with overgrowth of gram negative bacteria [19,21] . Bile salts have a detergent-like activity, which can make bacterial membranes permeable and can eventually lead to membrane collapse and cell damage [22] . Alternatively, bile salts are thought to prevent intestinal endotoxin and bacterial translocation by binding directly intraluminal endotoxin and bacteria, and creating poorly absorbed detergent-like complexes [23] .…”