Department of Genetics, University of Georgia, Athens, GA 30602, USA; Department of Food Science and Technology, Chung-Ang University, Anseong Gyeonggi 17546, Republic of Korea; Oak Ridge National Laboratory, The BioEnergy Science Center and the Center for Bioenergy Innovation, Oak Ridge, TN 37831, USA.
Department of Genetics, University of Georgia, Athens, GA 30602, USA; Oak Ridge National Laboratory, The BioEnergy Science Center and the Center for Bioenergy Innovation, Oak Ridge, TN 37831, USA.
Metab Eng. 2018 Sep;49:267-274. doi: 10.1016/j.ymben.2018.09.002. Epub 2018 Sep 5.
Polyamines are low molecular weight aliphatic nitrogen compounds found ubiquitously in microorganisms, plants, and animals. Spermidine is a common polyamine that plays a role in stabilizing chromatin, DNA replication, transcription, translation, as well as the regulation of cell growth and apoptosis in eukaryotes. Amines are also associated with defense to a number of environmental stresses including elevated temperature and have been shown to be involved in tolerance to fermentation inhibitors such as furan derivatives and acetic acid in Saccharomyces cerevisiae. While the tolerance and detoxifying mechanisms have been intensively studied, metabolic engineering efforts to construct tolerant and resistant strains have been few. Here we show that exogenously added spermidine confers enhanced tolerance to furans and acetic acid in the Gram-positive bacterium, Clostridium thermocellum. Deletion of the endogenous spermidine synthase resulted in a severe growth defect and hypersensitivity to both furans and acetic acid. Exogenously added spermidine rescued all three phenotypes. Overexpression of the endogenous spermidine synthase resulted in increased tolerance to these compounds without added spermidine. Increased tolerance to these fermentation inhibitors will facilitate the use of C. thermocellum, one of the most cellulolytic of all known bacterial species, for the production of fuels from plant biomass substrates.
多胺是广泛存在于微生物、植物和动物中的低分子量脂肪族含氮化合物。亚精胺是一种常见的多胺，它在稳定染色质、DNA 复制、转录、翻译以及真核生物细胞生长和凋亡的调控中发挥作用。胺类物质也与多种环境胁迫（包括高温）的防御有关，并且已经表明它们参与了对酿酒酵母中呋喃衍生物和乙酸等发酵抑制剂的耐受。虽然已经对耐受和解毒机制进行了深入研究，但构建耐受和抗性菌株的代谢工程努力却很少。在这里，我们表明，外源性添加亚精胺可增强革兰氏阳性菌热纤梭菌对呋喃和乙酸的耐受性。内源性亚精胺合酶的缺失导致严重的生长缺陷和对呋喃和乙酸的高度敏感。外源性添加亚精胺挽救了所有三种表型。内源性亚精胺合酶的过表达导致在没有添加亚精胺的情况下对这些化合物的耐受性增加。对这些发酵抑制剂的耐受性增加将促进热纤梭菌的使用，热纤梭菌是所有已知细菌物种中最具纤维素分解能力的细菌之一，用于从植物生物质底物生产燃料。
