Aono R
Department of Bioengineering, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Extremophiles. 1998 Aug;2(3):239-48. doi: 10.1007/s007920050066.
Water-immiscible organic solvents can be toxic to microorganisms. The tolerance levels differ among strains of Escherichia coli, suggesting that the organic solvent tolerance level is strain specific and determined genetically. We constructed several mutants from E. coli, of which the organic solvent tolerance levels were improved. The mutants were defective in the marR gene encoding a repressor protein for the mar operon that is responsible for environmental stress factors. High expression of stress-responsive genes, soxS, marA, and robA, elevated organic solvent tolerance levels of several strains of E. coli. These genes code for DNA-binding proteins that are transcriptional activators belonging to the AraC subfamily with the helix-turn-helix motif. It was shown that expression of the AcrAB-TolC system, a major efflux pump in E. coli, was positively regulated by the proteins. This system was highly expressed in the organic solvent-tolerant mutants. Strains defective in one of the genes, acrA, acrB, or tolC, were remarkably sensitive to organic solvents.
与水不混溶的有机溶剂可能对微生物有毒。不同大肠杆菌菌株的耐受水平有所不同，这表明有机溶剂耐受水平具有菌株特异性且由基因决定。我们从大肠杆菌构建了几个突变体，其有机溶剂耐受水平得到了提高。这些突变体在编码mar操纵子阻遏蛋白的marR基因中存在缺陷，该操纵子负责应对环境应激因素。应激反应基因soxS、marA和robA的高表达提高了几种大肠杆菌菌株的有机溶剂耐受水平。这些基因编码DNA结合蛋白，它们是属于具有螺旋-转角-螺旋基序的AraC亚家族的转录激活因子。结果表明，大肠杆菌中的主要外排泵AcrAB-TolC系统的表达受这些蛋白的正调控。该系统在有机溶剂耐受突变体中高度表达。在acrA、acrB或tolC基因之一中存在缺陷的菌株对有机溶剂非常敏感。
