OVERLAPS AND PARALLELS IN THE REGULATION OF INTRINSIC MULTIPLE-ANTIBIOTIC RESISTANCE IN ESCHERICHIA-COLI

Chromosomally encoded systems present in a variety of bacteria appear to play a central role in determining the intrinsic level of resistanc e to many commonly used antibiotics. Work with the Gram-negative bacte rium Escherichia coli has shown that there is significant similarity a t the amino acid sequence level among the structural components of the se resistance systems as well as among their genetic regulators. This review describes two of the better-studied regulatory systems, marRAB and soxRS, as well as two regulated multidrug-efflux systems, encoded by emrAB and acrAB, and focuses on conserved themes in their primary s tructures and environmental stimuli. The observed resistance to clinic ally important antibiotics appears to reflect an overlap with broad-ra nged adaptive responses by free-living bacteria to noxious plant mater ials in their natural environment.