objective(s): the major antibiotic efflux pump of esherichia coli is acrab-tolc. the first part of the pump, acrab, is encoded by acrab operon. the expression of this operon can be kept elevated by overexpression of an activator, mara following inactivation of marr and acrr repressors due to mutation in encoding genes, marr and acrr, respectively. the aims of this research were to use e. coli m...

  Objective(s): The major antibiotic efflux pump of Esherichia coli is AcrAB-TolC. The first part of the pump, AcrAB, is encoded by acrAB operon. The expression of this operon can be kept elevated by overexpression of an activator, MarA following inactivation of MarR and AcrR repressors due to mutation in encoding genes, marR and acrR, respectively. The aims of this research were to us...

MarA activates two membrane dependent mechanisms of resistance to different antibiotics, such as ciprofloxacin and tetracycline, including promotion of outflux and inhibition of influx of antibiotics. Thus, MarA causes multiple antibiotic resistance phenotype. The activation of these mechanisms needs overexpression of marA. This could happen through mutation in marR. Thus, the aim of this study...

MarA activates two membrane dependent mechanisms of resistance to different antibiotics, such as ciprofloxacin and tetracycline, including promotion of outflux and inhibition of influx of antibiotics. Thus, MarA causes multiple antibiotic resistance phenotype. The activation of these mechanisms needs overexpression of marA. This could happen through mutation in marR. Thus, the aim of this study...

mara activates two membrane dependent mechanisms of resistance to different antibiotics, such as ciprofloxacin and tetracycline, including promotion of outflux and inhibition of influx of antibiotics. thus, mara causes multiple antibiotic resistance phenotype. the activation of these mechanisms needs overexpression of mara. this could happen through mutation in marr. thus, the aim of this study...

Escherichia coli strain TP985, which has an insertional mutation in the gene for the periplasmic murein tripeptide binding protein MppA, was previously reported to overproduce MarA and exhibit a multiple-antibiotic resistance (Mar) phenotype (H. Li and J. T. Park, J. Bacteriol. 181:4842-4847, 1999). We found that TP985 contained a previously unrecognized marR mutation which was responsible for ...

OBJECTIVE(S) The major antibiotic efflux pump of Esherichia coli is AcrAB-TolC. The first part of the pump, AcrAB, is encoded by acrAB operon. The expression of this operon can be kept elevated by overexpression of an activator, MarA following inactivation of MarR and AcrR repressors due to mutation in encoding genes, marR and acrR, respectively. The aims of this research were to use E. coli mu...

The marRAB operon of Escherichia coli is self-repressed by MarR, while the MarA protein activates a number of promoters, including those for the AcrAB/TolC multidrug efflux pump (1, 4, 5). Inactivation of marR leads to a “Mar” multipleantibiotic resistance phenotype. In 1999, the mppA gene was reported to be a novel factor involved in the regulation of the marRAB operon (3). Strain TP985 had be...

A carbapenem-resistant clinical isolate of Escherichia coli, which lacked OmpF and OmpC porins, carried a marR mutation and expressed a functional yedS, a normally nontranslated gene. MarR and YedS are described here as having effects on the ability of this strain to resist carbapenems. Additionally, expression of YedS was regulated by the small RNA MicF in a MarA-dependent way. These findings ...

MarA activates two membrane dependent mechanisms of resistance to different antibiotics, such as ciprofloxacin and tetracycline, including promotion of outflux and inhibition of influx of antibiotics. Thus, MarA causes multiple antibiotic resistance phenotype. The activation of these mechanisms needs overexpression of marA. This could happen through mutation in marR. Thus, the aim of this study...