Biosciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, USA.
BMC Genomics. 2012 Jul 23;13:336. doi: 10.1186/1471-2164-13-336.
Clostridium thermocellum is a candidate consolidated bioprocessing biocatalyst, which is a microorganism that expresses enzymes for both cellulose hydrolysis and its fermentation to produce fuels such as lignocellulosic ethanol. However, C. thermocellum is relatively sensitive to ethanol compared to ethanologenic microorganisms such as yeast and Zymomonas mobilis that are used in industrial fermentations but do not possess native enzymes for industrial cellulose hydrolysis.
In this study, C. thermocellum was grown to mid-exponential phase and then treated with ethanol to a final concentration of 3.9 g/L to investigate its physiological and regulatory responses to ethanol stress. Samples were taken pre-shock and 2, 12, 30, 60, 120, and 240 min post-shock, and from untreated control fermentations for systems biology analyses. Cell growth was arrested by ethanol supplementation with intracellular accumulation of carbon sources such as cellobiose, and sugar phosphates, including fructose-6-phosphate and glucose-6-phosphate. The largest response of C. thermocellum to ethanol shock treatment was in genes and proteins related to nitrogen uptake and metabolism, which is likely important for redirecting the cells physiology to overcome inhibition and allow growth to resume.
This study suggests possible avenues for metabolic engineering and provides comprehensive, integrated systems biology datasets that will be useful for future metabolic modeling and strain development endeavors.
热纤梭菌是一种候选的综合生物加工生物催化剂，它是一种能够同时表达纤维素水解酶和发酵酶的微生物，可以将木质纤维素转化为燃料，如木质纤维素乙醇。然而，与工业发酵中使用的产乙醇微生物（如酵母和运动发酵单胞菌）相比，热纤梭菌对乙醇相对敏感，这些微生物虽然不具有用于工业纤维素水解的天然酶，但能够耐受乙醇。
在这项研究中，将热纤梭菌培养至指数中期，然后用乙醇处理至终浓度为 3.9 g/L，以研究其对乙醇胁迫的生理和调控反应。在冲击前、冲击后 2、12、30、60、120 和 240 分钟取样，并从未经处理的对照发酵液中取样，用于系统生物学分析。细胞生长被乙醇抑制，细胞内积累了碳源，如纤维二糖和糖磷酸，包括果糖-6-磷酸和葡萄糖-6-磷酸。热纤梭菌对乙醇冲击处理的最大反应是与氮吸收和代谢相关的基因和蛋白质，这可能对于重新引导细胞生理学以克服抑制并允许生长恢复至关重要。
这项研究为代谢工程提供了可能的途径，并提供了全面的、综合的系统生物学数据集，这将有助于未来的代谢建模和菌株开发工作。
