Impact of the RNA chaperone Hfq on multidrug resistance in Escherichia coli.
OBJECTIVE
Hfq is a bacterial RNA chaperone involved in the post-transcriptional regulation of many stress-inducible genes via small non-coding RNAs. Although Hfq is related to important phenotypes including virulence in many bacterial pathogens, its role in drug resistance is unknown. The aim of this study was to investigate the role of Hfq in bacterial multidrug resistance.


METHODS
The hfq gene was inactivated in Escherichia coli by use of pKO3, which is a gene replacement vector. The drug susceptibility and drug accumulation of the hfq mutant were determined. The level of production of the AcrB multidrug efflux pump in this mutant was also measured.


RESULTS
The hfq mutant was susceptible to acriflavine, benzalkonium, cefamandole, chloramphenicol, Crystal Violet, nalidixic acid, novobiocin, oxacillin and rhodamine 6G. E. coli cells were strongly stained with rhodamine 6G compared with the wild-type on deletion of hfq, indicating that Hfq affects the accumulation of the drug in bacterial cells. The deletion of the drug efflux gene acrB impairs the effect of hfq deletion on E. coli susceptibility. Furthermore, the level of AcrB protein production was reduced in the hfq mutant, whereas hfq deletion did not affect the promoter activity of the acrAB operon.


CONCLUSIONS
These results indicate that Hfq regulates the drug efflux system at the post-transcriptional level and reveals the previously uncharacterized role of Hfq in bacterial multidrug resistance.
Yamada
Junko
J
Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
Yamasaki
Seiji
S
Hirakawa
Hidetada
H
Hayashi-Nishino
Mitsuko
M
Yamaguchi
Akihito
A
Nishino
Kunihiko
K
D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology; D001693:Biological Transport, Active; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D035001:Host Factor 1 Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D035001:Host Factor 1 Protein; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012329:RNA, Bacterial; C083496:AcrB protein, E coli; C087373:Hfq protein, E coli