Gene ImrB of Corynebacterium glutamicum confers efflux-mediated resistanceto lincomycin

The lmrB gene of Corynebacterium glutamicum, which confers specific resista nce to lincosamides, such as lincomycin and clindamycin, was isolated. C. g lutamicum cells, carrying the lmrB gene in a multicopy plasmid, showed incr eased resistance to lincomycin with a MIC of 230 mug/ml, which is a 9-fold increase compared to that of the wild type. The lmrB-disrupted mutant becam e sensitive to the compound. No difference in sensitivity to erythromycin, penicillin G, tetracycline, chloramphenicol, spectinomycin, nalidixic acid, gentamicin, streptomycin, ethidium bromide, and sodium dodecyl sulfate was observed. The protonophore carbonyl cyanide m-chlorophenylhydrazone abolis hed the lincomycin-resistance of lmrB-carrying cells. The putative protein product of the gene contained 14-transmembrane regions and showed high amin o acid-sequence homology to the drug efflux pumps of other organisms. In ad dition, the putative protein contained a motif for major facilitators, sugg esting a role in efflux-mediated resistance to lincomycin.