Abstract
BackgroundLactic acid bacteria are commonly marketed as probiotics based on their putative or proven health-promoting effects. These effects are known to be strain specific but the underlying molecular mechanisms remain poorly understood. Therefore, unravelling the determinants behind probiotic features is of particular interest since it would help select strains that stand the best chance of success in clinical trials. Bile tolerance is one of the most crucial properties as it determines the ability of bacteria to survive in the small intestine, and consequently their capacity to play their functional role as probiotics. In this context, the objective of this study was to investigate the natural protein diversity within the Lactobacillus plantarum species with relation to bile tolerance, using comparative proteomics.ResultsBile tolerance properties of nine L. plantarum strains were studied in vitro. Three of them presenting different bile tolerance levels were selected for comparative proteomic analysis: L. plantarum 299 V (resistant), L. plantarum LC 804 (intermediate) and L. plantarum LC 56 (sensitive). Qualitative and quantitative differences in proteomes were analyzed using two-dimensional electrophoresis (2-DE), tryptic digestion, liquid chromatography-mass spectrometry analysis and database search for protein identification. Among the proteins correlated with differences in the 2-DE patterns of the bacterial strains, 15 have previously been reported to be involved in bile tolerance processes. The effect of a bile exposure on these patterns was investigated, which led to the identification of six proteins that may be key in the bile salt response and adaptation in L. plantarum: two glutathione reductases involved in protection against oxidative injury caused by bile salts, a cyclopropane-fatty-acyl-phospholipid synthase implicated in maintenance of cell envelope integrity, a bile salt hydrolase, an ABC transporter and a F0F1-ATP synthase which participate in the active removal of bile-related stress factors.ConclusionsThese results showed that comparative proteomic analysis can help understand the differential bacterial properties of lactobacilli. In the field of probiotic studies, characteristic proteomic profiles can be identified for individual properties that may serve as bacterial biomarkers for the preliminary selection of strains with the best probiotic potential.
Highlights
Lactic acid bacteria are commonly marketed as probiotics based on their putative or proven healthpromoting effects
The selected strains were cultured in non-stressing conditions so as to investigate their inherent proteome differences, with a specific focus on proteins that may play a role in bile tolerance processes
This approach showed that the natural protein diversity among L. plantarum strains cultured in standard conditions can reflect their ability to tolerate bile
Summary
Lactic acid bacteria are commonly marketed as probiotics based on their putative or proven healthpromoting effects These effects are known to be strain specific but the underlying molecular mechanisms remain poorly understood. Lactic acid bacteria (LAB) are indigenous inhabitants of the human GI tract [6] They have a long history of traditional use in many industrial and artisanal plant, meat, and dairy fermentations. Scientific evidence that would help understand the mechanisms behind the activities of probiotics and narrow down the expensive and time-consuming clinical trials to strains that stand the best chance of success are of great interest. Such evidence may include data from epidemiological studies, from in vivo and in vitro trials, as well as from mechanistic, genomic and proteomic studies
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