Active efflux of bile salts by Escherichia coli

The ability of Escherichia coli to resist high levels of bile salts was analyzed to presence of an energy-dependent efflux mechanism for bile salts in the outer membrane barrier of gram-negative bacteria. The deenergization of the cytoplasmic membrane of intact Escherichia coli cells by a proton conductor induced the intracellular accumulation of bile salts. Furthermore, intact Escherichia coli cells exhibited an energy-dependent prevention of chenodeoxycholate and taurocholate accumulation.