RESUMO
Plasmid-carried qnrS1 is derived from Vibrio splendidus chromosomal qnrVS1. qnrVS1 transcripts increased 21- to 34-fold with subinhibitory concentrations of ciprofloxacin but much less with mitomycin. No LexA binding sites were upstream of qnrS1 or qnrVS1, and similar induction levels were observed in lexA-positive and lexA-negative Escherichia coli strains with native qnrS1 plasmid pMG306 but not with pUC18-cloned qnrS1 or qnrVS1. Thus, qnrS1 induction by quinolones is independent of the SOS system and requires sequence besides that of the structural gene.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/efeitos dos fármacos , Proteínas de Escherichia coli/efeitos dos fármacos , Plasmídeos/genética , Quinolonas/farmacologia , Resposta SOS em Genética/efeitos dos fármacos , Vibrio/efeitos dos fármacos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Ciprofloxacina/farmacologia , Farmacorresistência Bacteriana/genética , Escherichia coli/efeitos dos fármacos , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Humanos , Testes de Sensibilidade Microbiana , Mitomicina/farmacologia , Vibrio/genéticaRESUMO
Plasmid-carried quinolone resistance genes, like qnrA, are widespread in Enterobacteriaceae. To gain insight into its little-understood native functions, we studied the effect of environmental conditions on chromosomal qnrA expression in Shewanella algae. Among conditions of DNA damage, oxidative and osmotic stress, starvation, heat, and cold, only cold shock increased gene expression, as measured by quantitative reverse transcription-PCR (qRT-PCR). Induction was graded and occurred during growth arrest, suggesting that qnrA may contribute to the adaptation of Shewanella to low temperatures.
