REGULATION OF THE PERMEABILITY OF THE GONOCOCCAL CELL-ENVELOPE BY THEMTR SYSTEM

The mtrR gene of Neisseria gonorrhoeae controls the level of susceptib ility to hydrophobic antibiotics and detergents. The mtrR gene was clo ned and shown to encode a putative transcriptional repressor. The mtr region was homologous to the envCD and acrAB regions of Escherichia co li, which are also involved in susceptibility to hydrophobic compounds . A homelogous repressor protein was encoded by a previously unrecogni zed open reading frame within both the envCD and acrAB regions. Deleti on of mtrR resulted in increased resistance to antibiotics and deterge nts: the mtrR mutations in two penicillin-resistant clinical isolates resulted in a change of His-105 to Tyr. We propose that the mtrR repre ssor allows gonococci to regulate the permeability of its cell envelop e in response to environmental signals, so that they can grow in the p resence of toxic faecal lipids in the rectum as well as in the genital tract.