Proteomic analysis to unravel bile acid response of a probiotic Lactobacillus reuteri strain

BUSTOS, A. Y.; FONT DE VALDEZ, G.; FADDA, S.; MOZZI, F.; RAYA, R.; TARANTO, M. P.

Egmond aan Zee

Simposio; X Symposium on lactic acid bacteria; 2011

Lactobacillus (L.) reuteri is an established probiotic agent; the most widely distributed Lactobacillus species among mammalians. The ability of L. reuteri to survive passage through the intestinal tract is a key point related to its probiotic function. Aiming at unraveling the molecular basis of the adaptive mechanism of L. reuteri CRL1098 to bile acids (BA), a proteomic approach was carried out. Protein expression of L. reuteri CRL 1098 growing in the presence of BA (glycodeoxycholic; GDCA or deoxycholic; DCA) was evaluated using bidimensional electrophoresis and mass spectrometry. A delay in bacterial growth was observed only when cells were challenged with DCA. Proteomic data showed that in the presence of GDCA, 14 proteins related to amino acid and nucleotide metabolisms, transcription and translation and pH homeostasis were overexpressed. Although 8 proteins involved mainly in lipid metabolism were synthesized in lower amounts. When L. reuteri CRL1098 was grown in the presence of DCA, 13 proteins, including chaperones and enzymes from amino acid pathways were up-regulated, while 15 from nucleotide synthesis, energetic and lipid metabolisms were under-shifted. The better adaptation observed in the presence of GDCA could be related to an improved pH homeostasis due to the overexpression of GTP-binding protein TypA and nucleotide metabolism proteins such as CTP synthetase. On the contrary the later was underexpressed in DCA growing conditions. The stronger harsh environment produced by DCA is reflected by the overexpression of a typical stress proteins such as chaperone GroEL Results showed that bile salts induce a complex physiological response in L. reuteri CRL 1098, this study contributing with new insights in the mechanisms underlying the capacity of intestinal lactobacilli to tolerate bile stress.