Beta-lactam resistance modulated by the overexpression of response regulators of two-component signal transduction systems in Escherichia coli.
OBJECTIVE
In Escherichia coli, there are 32 open reading frames assumed, on the basis of sequence similarities, to be response regulator genes of two-component signal transduction systems. We cloned all 32 response regulators and examined whether or not response regulator-overexpressing cells confer resistance to beta-lactam antibiotics in E. coli.


METHODS
E. coli KAM3 (acrB), a drug-hypersusceptible mutant, was used as a host strain for the overproduction of response regulators. MICs were determined by the agar dilution method.


RESULTS
Thirteen response regulators out of 32 genes, namely baeR, cheY, cpxR, creB, evgA, fimZ, narL, ompR, rcsB, rstA, yedW, yehT and dcuR, conferred increased beta-lactam resistance. Among them, overexpression of baeR, evgA, rcsB and dcuR conferred high-level resistance. The baeR- and evgA-mediated resistance is due to up-regulation of the expression of multidrug exporter genes, acrD and mdtABC for baeR, and yhiUV for evgA, because baeR- and evgA-mediated resistance was completely absent in strains lacking these exporter genes. The fimZ-mediated cefalothin resistance is due to the chromosomal ampC gene, because the ampC deletion strain did not show fimZ-mediated resistance.


CONCLUSIONS
Two-component signal transduction systems contribute to beta-lactam resistance in E. coli. Multidrug exporters play roles in two-component signal transduction system-mediated beta-lactam resistance.
Hirakawa
Hidetada
H
Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
Nishino
Kunihiko
K
Yamada
Junko
J
Hirata
Takahiro
T
Yamaguchi
Akihito
A
D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D008074:Lipoproteins / Q000096:biosynthesis / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D008826:Microbial Sensitivity Tests / Q000379:methods; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D016366:Open Reading Frames / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D014157:Transcription Factors; D001618:beta-Lactamases; C083497:AcrA protein, E coli; C083496:AcrB protein, E coli; C065601:BvgA protein, Bacteria; C489314:EvgA protein, E coli; C434281:Mdt-A protein, E coli; C048795:AmpC beta-lactamases