Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China.
Int J Biochem Cell Biol. 2012 Jul;44(7):1087-96. doi: 10.1016/j.biocel.2012.03.017. Epub 2012 Apr 4.
During the fermentation process, Saccharomyces cerevisiae cells are often inhibited by the accumulated ethanol, and the mechanism of the S. cerevisiae response to ethanol is not fully understood. In the current study, a systematic analytical approach was used to investigate the changes in the S. cerevisiae cell metabolome that were elicited by treatment with various concentrations of ethanol. Gas chromatography-mass spectrometry and a multivariate analysis were employed to investigate the ethanol-associated intracellular biochemical changes in S. cerevisiae. The intracellular metabolite profiles that were found upon treatment of the cells with different concentrations of ethanol were unique and could be distinguished with the aid of principal component analysis. Furthermore, partial least-squares-discriminant analysis revealed a group classification and pairwise discrimination between the control without ethanol and ethanol treated groups, and 29 differential metabolites with variable importance in the projection value greater than 1 were identified, which was also confirmed by the subsequent hierarchical cluster analysis. The metabolic relevance of these compounds in the response of S. cerevisiae to ethanol stress was investigated. Under ethanol stress, the glycolysis was inhibited and the use of carbon sources for fermentation was diminished, which might account for the growth inhibition of S. cerevisiae cells. It was suggested that S. cerevisiae cells change the levels of fatty acids, e.g., hexadecanoic, octadecanoic and palmitelaidic acids, to maintain the integrity of their plasma membrane through decreasing membrane fluidity in the medium containing ethanol. Moreover, the increased levels of some amino acids idemtified in the cells of ethanol-treated experimental group might also confer ethanol tolerance to S. cerevisiae. These results reveal that the metabolomics strategy is a powerful tool to gain insight into the molecular mechanism of a microorganism's cellular response to environmental stress factors.
在发酵过程中，酿酒酵母细胞经常受到积累的乙醇的抑制，并且乙醇对酿酒酵母的响应机制尚未完全阐明。在当前的研究中，使用系统分析方法研究了不同浓度乙醇处理对酿酒酵母细胞代谢组的变化。气相色谱-质谱联用和多元分析用于研究乙醇处理后酿酒酵母细胞内的生化变化。在用不同浓度乙醇处理细胞时，发现细胞内代谢物图谱是独特的，可以通过主成分分析来区分。此外，偏最小二乘判别分析显示了无乙醇对照和乙醇处理组之间的分组分类和两两区分，并且确定了 29 种具有投影变量重要性大于 1 的差异代谢物，随后的层次聚类分析也证实了这一点。研究了这些化合物在酿酒酵母对乙醇胁迫响应中的代谢相关性。在乙醇胁迫下，糖酵解受到抑制，发酵中对碳源的利用减少，这可能是酿酒酵母细胞生长受到抑制的原因。研究表明，酿酒酵母细胞通过降低含乙醇介质中膜的流动性，改变脂肪酸（如十六烷酸、十八烷酸和棕榈烯酸）的水平，以维持其质膜的完整性。此外，在乙醇处理实验组细胞中鉴定出的一些氨基酸水平的增加也可能赋予酿酒酵母对乙醇的耐受性。这些结果表明，代谢组学策略是深入了解微生物细胞对环境应激因子的分子机制的有力工具。
