Department of Genetics, Faculty of Science and Biotechnology Center, University of Shahrekord, Shahrekord, Iran.
students in Genetics at University of Shahrekord.
Iran J Basic Med Sci. 2013 Dec;16(12):1254-8.
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.
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 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.
The effect of marR or acrR mutation on acrAB overexpression is dependent on levels of resistance to tetracycline and ciprofloxacin.
大肠埃希菌的主要抗生素外排泵是 AcrAB-TolC。泵的第一部分，AcrAB，由 acrAB 操纵子编码。由于编码基因 marR 和 acrR 分别发生突变，导致 MarR 和 AcrR 抑制剂失活，激活剂 MarA 的过度表达可以使该操纵子的表达保持升高。本研究的目的是使用 marR 突变或无突变的大肠埃希菌突变体，寻找 acrR 中可能存在的突变，并定量测定 acrAB 的表达。
通过 PCR 扩增这些突变体中 acrR 基因的 DNA 结合区，并进行测序。通过实时 PCR 测定 acrA 和 acrB 的相对表达。
结果表明，W26 和 C14 在 acrR 中具有相同的突变，但与野生型菌株相比，没有一个突变体过度表达 acrA 和 acrB。
marR 或 acrR 突变对 acrAB 过度表达的影响取决于对四环素和环丙沙星的耐药水平。
