Solventogenic clostridia are an important class of microorganisms that can produce various biofuels. One of the bottlenecks in engineering clostridia stems from the fact that central metabolic pathways remain poorly understood. Here, we utilized the power of (13) C-based isotopomer analysis to re-examine central metabolic pathways of Clostridium acetobutylicum ATCC 824. We demonstrate using [1,2-(13) C]glucose, MS analysis of intracellular metabolites, and enzymatic assays that C. acetobutylicum has a split TCA cycle where only Re-citrate synthase (CS) contributes to the production of α-ketoglutarate via citrate. Furthermore, we show that there is no carbon exchange between α-ketoglutarate and fumarate and that the oxidative pentose-phosphate pathway (oxPPP) is inactive. Dynamic gene expression analysis of the putative Re-CS gene (CAC0970), its operon, and all glycolysis, pentose-phosphate pathway, and TCA cycle genes identify genes and their degree of involvement in these core pathways that support the powerful primary metabolism of this industrial organism.

中文翻译：

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解析丙酮丁醇梭菌 ATCC 824 的 TCA 循环和戊糖-磷酸途径：同位素分析、体外活性和表达分析。

产溶剂梭菌是一类重要的微生物，可以生产各种生物燃料。工程梭菌的瓶颈之一源于对中心代谢途径仍然知之甚少的事实。在这里，我们利用基于 (13) C 的同位素分析的强大功能重新检查丙酮丁醇梭菌 ATCC 824 的中心代谢途径。 我们展示了使用 [1,2-(13) C] 葡萄糖、细胞内代谢物的 MS 分析和酶分析表明，丙酮丁醇梭菌具有分裂的 TCA 循环，其中只有再柠檬酸合酶 (CS) 有助于通过柠檬酸盐产生 α-酮戊二酸。此外，我们表明α-酮戊二酸和富马酸之间没有碳交换，并且氧化戊糖-磷酸途径（oxPPP）是不活跃的。假定的 Re-CS 基因 (CAC0970) 的动态基因表达分析，