Proteomic and transcriptomic analysis of the response to bile stress of Lactobacillus casei BL23.

Lactobacillus casei is a lactic acid bacterium commonly found in the gastrointestinal tract of animals, and some strains are used as probiotics. The ability of probiotic strains to survive the passage through the gastrointestinal tract is considered a key factor for their probiotic action. Therefore, tolerance to bile salts is a desirable feature for probiotic strains. In this study we have characterized the response of L. casei BL23 to bile by a transcriptomic and proteomic approach. The analysis revealed that exposure to bile induced changes in the abundance of 52 proteins and the transcript levels of 67 genes. The observed changes affected genes and proteins involved in the stress response, fatty acid and cell wall biosynthesis, metabolism of carbohydrates, transport of peptides, coenzyme levels, membrane H(+)-ATPase, and a number of uncharacterized genes and proteins. These data provide new insights into the mechanisms that enable L. casei BL23 to cope with bile stress.