title: Effect of overexpression of small non-coding DsrA RNA on multidrug efflux in Escherichia coli.
abstract: OBJECTIVE
  Several putative and proven drug efflux pumps are present in Escherichia coli. Because many such efflux pumps have overlapping substrate spectra, it is intriguing that bacteria, with their economically organized genomes, harbour such large sets of multidrug efflux genes. To understand how bacteria utilize these multiple efflux pumps, it is important to elucidate the process of pump expression regulation. The aim of this study was to determine a regulator of the multidrug efflux pump in this organism.
  
  
  METHODS
  We screened a genomic library of E. coli for genes that decreased drug susceptibility in this organism. The library was developed from the chromosomal DNA of the MG1655 strain, and then the recombinant plasmids were transformed into an acrB-deleted strain. Transformants were screened for resistance to various antibiotics including oxacillin.
  
  
  RESULTS
  We found that the multidrug susceptibilities of the acrB-deleted strain were decreased by the overexpression of small non-coding DsrA RNA as well as by the overexpression of known regulators of multidrug efflux pumps. Plasmids carrying the dsrA gene conferred resistance to oxacillin, cloxacillin, erythromycin, rhodamine 6G and novobiocin. DsrA decreased the accumulation of ethidium bromide in E. coli cells. Furthermore, expression of mdtE was significantly increased by dsrA overexpression, and the decreased multidrug susceptibilities modulated by DsrA were dependent on the MdtEF efflux pump.
  
  
  CONCLUSIONS
  These results indicate that DsrA modulates multidrug efflux through activation of genes encoding the MdtEF pump in E. coli.
authors.affiliation: Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-047, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Nishino
authors.forename: Seiji
authors.initials: S
authors.lastname: Yamasaki
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Hayashi-Nishino
authors.forename: Akihito
authors.initials: A
authors.lastname: Yamaguchi
mesh_terms: D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000187:drug effects / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000187:drug effects / Q000235:genetics; D010068:Oxacillin / Q000378:metabolism / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D058727:RNA, Small Untranslated; D022661:RNA, Untranslated / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010068:Oxacillin; D058727:RNA, Small Untranslated; D022661:RNA, Untranslated; C083496:AcrB protein, E coli; C405431:DsrA RNA, E coli; C477834:MdtE protein, E coli; C477833:MdtF protein, E coli