Studying probiotics - polyphenols interplay by proteomics

Lactobacilli are essential components of gut microflora and some strains exhibit probiotic features. In the gut, they participate to the metabolism of food components such as polyphenols, molecules that have well-known nutraceutical properties and positively affect microbiota composition by inhibiting pathogens and favoring probiotic growth [1]. Polyphenols-microbiota interplay was investigated by proteomics using as model system the potential probiotic strain Lactobacillus acidophilus DSMZ20079 grown in presence/absence of rutin (quercetin-3-rutinoside), one of the glycosylated forms of quercetin, that is among the most studied polyphenols [2]. Proteomics highlighted that molecular chaperones, Clp ATP-dependent proteases, oxidoreductases, responsible of cell redox homeostasis, and enzymes involved in energy metabolism were overexpressed in cells grown in the presence of rutin. The activation of glycolysis led to an increase of ATP production, needed to sustain ATP-dependent activity of folding and degradation machinery. Therefore, adaptation of L. acidophilus to the presence of rutin could be related to its ability to activate general stress response mechanisms. Interestingly, the activation of pyruvate kinase could parallel with the higher expression of branched-chain amino acid aminotransferase. In fact, pyruvate could be converted to ?-ketoacids and finally, by the aminotransferases action, into branched-chain amino acids, that are precursors of short chain fatty acids [3]. These molecules, produced by microbial metabolism in the gut, contribute in maintaining host homeostasis and positively act on gut inflammatory disorders. This work represents one of the first proteomic study focused on the investigation of the complex bacteria-polyphenols-interplay and further assesses the key role of proteomics in the elucidation of molecular mechanisms underlying probiotic traits.