Role of multiple efflux pumps in Escherichia coli in indole expulsion

Escherichia coli chromosome encodes several multidrug transporters. Despite their protective function against antibacterial agents, the specific physi ological actions of these transporters are not fully understood. E. coli pr oduces indole, a metabolite of tryptophan, under physiological conditions. Defined inactivation of the acrEF gene, the product of which is known as an energy-dependent multiple drug efflux pump, decreased indole excretion whi le reintroduction of the acrEF gene restored it. A Delta acrEF mutant accum ulated more intracellular indole than the parent. This mutant was more susc eptible to the growth-inhibitory effect of indole than the parent. These re sults indicate that the AcrEF system plays a significant role in indole eff lux. (C) 1999 Federation of European Microbiological Societies. Published b y Elsevier Science B.V. All rights reserved.