梭菌适应胁迫新策略

梭菌（Clostridium）是一类与人类关系十分密切的革兰氏阳性细菌。理解梭菌适应环境胁迫的机制，无论是对在医学上控制梭菌，还是在工业上利用梭菌，都具有十分重要的意义。

梭菌属中在工业上最广泛应用的种是丙酮丁醇梭菌。丙酮丁醇梭菌的正常发酵过程要经过产酸和产溶剂两个阶段，其中从产酸向产溶剂阶段的过渡，通常被认为是该菌的一种解毒和适应机制。在这一转换过程中，许多与胁迫应答、溶剂合成相关的蛋白会上调表达，而与氨基酸和蛋白质合成相关的蛋白则会下调表达。

为了更好理解丙酮丁醇梭菌适应环境胁迫的机制，研究人员模拟自然界的进化过程，获得了一株能够在丁醇浓度提高50%的胁迫环境下正常生长的突变株。采用比较蛋白质组分析，研究人员发现突变株中70%本应在产溶剂阶段上调或下调表达的差异蛋白，在产酸期就提前上调或下调，在产溶剂期还会进一步增大上调或下调的幅度。这表明突变株进化出了一种适应环境胁迫的新策略，即其解毒和适应机制能够更敏感地感知胁迫信号，提前启动并增强对关键蛋白的调控能力，更快、更灵活地调整细胞生理状态，从而帮助突变株适应了更具挑战的环境。

相关工作已于4月29日在线发表在美国化学会《蛋白质组学研究》（Journal of Proteome Research）上。该研究还建立了梭菌属的第一张蛋白质组参考图谱，为梭菌属的蛋白质组学研究提供了基础数据。

该研究由博士生毛绍名在李寅研究员和张延平博士的指导下完成，研究得到973计划、中国科学院知识创新工程重要方向项目和中国科学院创新团队国际合作伙伴计划资助。

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Proteome Reference Map and Comparative Proteomic Analysis between a Wild Type Clostridium acetobutylicum DSM 1731 and its Mutant with Enhanced Butanol Tolerance and Butanol Yield
Shaoming Mao, Yuanming Luo, Tianrui Zhang, Jinshan Li, Guanhui Bao, Yan Zhu, Zugen Chen, Yanping Zhang, Yin Liand Yanhe Ma

Institute of Microbiology, Chinese Academy of Sciences, Beijing, China, Graduate School of Chinese Academy of Sciences, Beijing, China, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China, and Department of Human Genetics, School of Medicine, University of California, Los Angeles, California 90095

【Abstract】The solventogenic bacterium Clostridium acetobutylicum is an important species of the Clostridium community. To develop a fundamental tool that is useful for biological studies of C. acetobutylicum, we established a high resolution proteome reference map for this species. We identified 1206 spots representing 564 different proteins by mass spectrometry, covering approximately 50% of major metabolic pathways. To better understand the relationship between butanol tolerance and butanol yield, we performed a comparative proteomic analysis between the wild type strain DSM 1731 and the mutant Rh8, which has higher butanol tolerance and higher butanol yield. Comparative proteomic analysis of two strains at acidogenic and solventogenic phases revealed 102 differentially expressed proteins that are mainly involved in protein folding, solvent formation, amino acid metabolism, protein synthesis, nucleotide metabolism, transport, and others. Hierarchical clustering analysis revealed that over 70% of the 102 differentially expressed proteins in mutant Rh8 were either upregulated (e.g., chaperones and solvent formation related) or downregulated (e.g., amino acid metabolism and protein synthesis related) in both acidogenic and solventogenic phase, which, respectively, are only upregulated or downregulated in solventogenic phase in the wild type strain. This suggests that Rh8 cells have evolved a mechanism to prepare themselves for butanol challenge before butanol is produced, leading to an increased butanol yield. This is the first report on the comparative proteome analysis of a mutant strain and a base strain of C. acetobutylicum. The fundamental proteomic data and analyses will be useful for further elucidating the biological mechanism of butanol tolerance and/or enhanced butanol production.