Division of Applied Life Science (Brain Korea 21 Program), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, 900 Gajwadong, Jinju, Republic of Korea.
J Biosci Bioeng. 2013 Mar;115(3):253-8. doi: 10.1016/j.jbiosc.2012.10.009. Epub 2012 Nov 16.
Improvement of a microorganism's tolerance against organic solvents is required for a microbial factory producing terpenoid based biofuels. The bacterial genes, marA, imp, cls and cti have been found to increase organic solvent tolerance. Thus, the tolerance against the following terpenoids (isopentenol, geraniol, myrcene, and farnesol) was studied with overexpression of marA, imp, cls and cti genes in Escherichia coli. The marA overexpression significantly enhanced the tolerance of E. coli against geraniol, whereas there was no tolerance improvement against the terpenoids by overexpression of cls and cti genes. The imp overexpression even yielded sensitive phenotype to the tested solvents. The colony forming efficiency of the marA overexpressing E. coli was increased by 10(4)-fold in plate overlay of geraniol compared to that of wild type E. coli and a two-fold decrease of intracellular geraniol accumulation was also observed in liquid culture of geraniol. Single knock-out mutations of marA, or one of the following genes (acrA, acrB and tolC) encoding AcrAB-TolC efflux pump made E. coli hypersensitive to geraniol. The geraniol tolerance conferred by marA overexpression was attributed to the AcrAB-TolC efflux pump that is activated by MarA.
为了生产基于萜烯的生物燃料的微生物工厂，需要提高微生物对有机溶剂的耐受性。已经发现细菌基因 marA、imp、cls 和 cti 可以提高有机溶剂耐受性。因此，通过过表达 marA、imp、cls 和 cti 基因，研究了大肠杆菌对以下萜烯（异戊烯醇、香叶醇、月桂烯和法呢醇）的耐受性。过表达 marA 显著增强了大肠杆菌对香叶醇的耐受性，而过表达 cls 和 cti 基因对萜烯没有耐受性提高。imp 过表达甚至对测试溶剂产生了敏感表型。与野生型大肠杆菌相比，过表达 marA 的大肠杆菌在香叶醇平板覆盖物中的集落形成效率提高了 10^4 倍，在香叶醇液体培养中也观察到细胞内香叶醇积累减少了两倍。marA 的单敲除突变，或编码 AcrAB-TolC 外排泵的以下基因（acrA、acrB 和 tolC）之一的敲除突变，使大肠杆菌对香叶醇敏感。marA 过表达赋予的香叶醇耐受性归因于由 MarA 激活的 AcrAB-TolC 外排泵。
