expression of acra and acrb genes in esherichia coli mutants with or without marr or acrr mutations

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 mutants with or without mutation in marr to search for the presence of possible mutation in acrr and to quantify the expression of acrab .   materials and methods: the dna binding region of acrr gene in these mutants were amplified by pcr and sequenced. the relative expression of acra and acrb were determined by real time pcr. results: results showed that w26 and c14 had the same mutation in acrr, but none of the mutants overexpressed acra and acrb in comparison with wild type strain.   conclusions: the effect of marr or acrr mutation on acrab overexpression is dependent on levels of resistance to tetracycline and ciprofloxacin.