Probably part of an efflux pump system that contributes to adaptation to osmotic stress and resistance to colistin. Cotranscribed with emrA. Induced during osmotic stress. Deletion of the gene significantly slows cell growth in 20% sucrose. The mutant is more susceptible to colistin, nafcillin, paromomycin, spiramycin and D,L-serine hydroxamate than the wild type. Belongs to the major facilitator superfamily. EmrB family.