Cholic acid is accumulated spontaneously, driven by membrane deltapH, in many lactobacilli

Abstract

Many lactobacilli from various origins were found to apparently lack cholic acid extrusion activity. Cholic acid was accumulated spontaneously, driven by the transmembrane proton gradient. Accumulation is a newly identified kind of interaction between intestinal microbes and unconjugated bile acids and is different from extrusion and modification, which have been described previously.

FIG. 1

Transport of CA by L. salivarius subsp. salicinius JCM 1044 (A) and L. acidophilus JCM 1028 (B) in the presence of ionophores. De-energized, washed cells were incubated at pH 7.0 with [¹⁴C]CA in the absence (■) and presence (●) of glucose and after the addition of valinomycin (Val; ▵) or nigericin (Nig; ▿). Ionophores were added 5 min (A) or 7 min (B) after the first glucose addition (1st Glc). A second addition of glucose (2nd Glc; ○) was performed 15 min (A) or 25 min (B) after the first addition of glucose. CA* denotes both cholic acid and cholate anion.

FIG. 2

Accumulation of CA by JCM 1044 at different external pH values. The experiments were carried out at different pH values: 7.6 (◊), 7.3 (▵), 7.0 (●), 6.6 (▴), and 6.2 (⧫). For energization of the cells, glucose was added at t = 15 min. CA amounts in the nonenergized cells are demonstrated by only one line (■), since these were very similar at all pH values tested. CA* denotes both cholic acid and cholate anion.