Mutation in a locus linked to penB-nmp causes suppression of the Mtr phenotype of Neisseria gonorrhoeae

Abstract

The chromosomal locus mtr, which encodes low-level resistance to multiple antibacterial agents in Neisseria gonorrhoeae, is subject to phenotypic suppression by env mutations that increase the permeability of the envelope. We have identified a new locus, mom (for modifier of Mtr), which is located on the chromosome very close to penB and nmp, loci known to be linked to each other and to spc. Phedotypic suppression of Mtr was recognized by reductions of resistance to benzylpenicillin and also to oxacillin and the hydrophobic agents novobiocin and erythromycin. The resistance to each of these antibiotics returned to the Mtr levels in mom' transformants isolated by selection for increased resistance to either novobiocin or erythromycin; the accompanying change of the outer membrane protein I seroreactions confirmed the proximity of nmp and mom.