Molecular cloning and characterization of a multidrug efflux pump, SmfY, from Serratia marcescens

We cloned a gene smfY for multidrug efflux pump from chromosomal DNA of Serratia marcescens using drug-hypersensitive Escherichia coli KAM32 as the host, and characterized the pump. E. coli KAM32/pESM42 carrying the smfY showed significantly increased MICs of various drugs including DAPI, norfloxacin, benzalkonium chloride, acriflavine and ethidium bromide, compared with the control. We also detected energy-dependent ethidium and acriflavine efflux due to the SmfY. Sequence analysis revealed that the SmfY was a multidrug ef-flux pump of the MF (Major Facilitator) superfamily transporters. This is the first report of a multidrug efflux pump belonging to the MF superfamily in S. marcescens.