Analysis of a complete library of putative drug transporter genes in Escherichia coli

The complete sequencing of bacterial genomes has revealed a large number of drug transporter genes. In Escherichia coli, there are 37 open reading fra mes (ORFs) assumed to be drug transporter genes on the basis of sequence si milarities, although the transport capabilities of most of them have not be en established yet. We cloned all 37 putative drug transporter genes in E. coli and investigated their drug resistance phenotypes using an E. coli dru g-sensitive mutant as a host. E. coli cells transformed with a plasmid carr ying one of 20 ORFs, i.e.,fsr, mdfA, yceE, yceL, bcr, emrKY, emrAB, emrD, y idY, yjiO, ydhE, acrAB, cusA (formerly ybdE), yegMNO, acrD, acrEF, yhiUV, e mrE, ydgFE, and ybjYZ, exhibited increased resistance to some of the 26 rep resentative antimicrobial agents and chemical compounds tested in this stud y. Of these 20 ORFs, cusA, yegMNO, ydgFE, yceE, yceL, yidY, and ybjYZ are n ovel drug resistance genes. The fsr, bcr, yjiO, ydhE, acrD, and yhiUV genes gave broader resistance spectra than previously reported.