Active excretion of bile acids in Lactobacillus reuteri CRL 1098 is mediated by ATP

BUSTOS, AY; RAYA, R; FONT DE VALDEZ, G; TARANTO, MP

BIOTECHNOLOGY LETTERS

SPRINGER

Lugar: Berlin; Año: 2011 p. 2265 - 2269

0141-5492

Purpose of work To study whether an active bile acid (BA) efflux occurs in Lactobacillus reuteri CRL 1098 as well as the nature (ATP or proton motiveforce [PMF] mediated primary transport) of the BA extrusion mechanism.BAs are powerful detergents which disorganize the lipid bilayer structure of cellular membranes. Specific bile resistance mechanisms (bile efflux, bile salthydrolysis, and intrinsic architecture and composition of cell membrane the most prevalent) have been described in intestinal bacteria. L. reuteri, showed asignificant degree of resistance to the toxic action of BA and the presence of an active efflux ATPdependent of conjugated (taurocholic [TCA]) and free (cholic [CA]) BA in the CRL 1098 strain is now reported. However, due the high pKa (5.5) of cholic acid (CA) compared with the conjugated species, a significant fraction (between 35 and 50% at pH 6.5 and 5.2, respectively) of free BA also diffusedpassively, even in the absence of ATP. To our knowledge, our results represent the first evidence of ATP as the energy source involved in the BA extrusion in L. reuteri.