Bacillus thuringiensis is the most widely used eco-friendly biopesticide, containing two primary determinants of biocontrol, endospore and insecticidal crystal proteins (ICPs). The 2-methylcitrate cycle is a widespread carbon metabolic pathway playing a crucial role in channelling propionyl-CoA, but with poorly understood metabolic regulatory mechanisms. Here, we dissect the transcriptional regulation of the 2-methylcitrate cycle operon prpCDB and report its unprecedented role in controlling the sporulation process of B. thuringiensis. We found that the transcriptional activity of the prp operon encoding the three critical enzymes PrpC, PrpD, and PrpB in the 2-methylcitrate cycle was negatively regulated by the two global transcription factors CcpA and AbrB, while positively regulated by the LysR family regulator CcpC, which jointly account for the fact that the 2-methylcitrate cycle is specifically and highly active in the stationary phase of growth. We also found that the prpD mutant accumulated 2-methylcitrate, the intermediate metabolite of the 2-methylcitrate cycle, which delayed and inhibited sporulation at the early stage. Thus, our results not only revealed sophisticated transcriptional regulatory mechanisms for the metabolic 2-methylcitrate cycle but also identified 2-methylcitrate as a novel regulator of sporulation in B. thuringiensis.

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2-柠檬酸甲酯循环：芽孢杆菌芽孢形成的调控良好的控制器。

苏云金芽孢杆菌是使用最广泛的生态友好型生物农药，包含两个主要的生物防治决定因素：内生孢子和杀虫晶体蛋白（ICPs）。2-甲基柠檬酸循环是一个广泛的碳代谢途径，在引导丙酰辅酶A的过程中起着至关重要的作用，但对代谢调节机制的了解却很少。在这里，我们解剖2-甲基柠檬酸周期操纵子prpCDB的转录调控，并报告其在控制苏云金芽孢杆菌孢子形成过程中的空前作用。我们发现，在2-甲基柠檬酸循环中，编码三个关键酶PrpC，PrpD和PrpB的prp操纵子的转录活性受到两个全局转录因子CcpA和AbrB的负调控，而被LysR家族调控子CcpC负调控，这共同解释了一个事实，即2-甲基柠檬酸循环在生长的稳定期具有特定的高度活跃性。我们还发现prpD突变体积累了2-甲基柠檬酸，这是2-甲基柠檬酸循环的中间代谢产物，它在早期延迟并抑制了孢子形成。因此，我们的结果不仅揭示了代谢2-甲基柠檬酸循环的复杂转录调控机制，而且还确定了2-甲基柠檬酸是苏云金芽孢杆菌中新的孢子形成调节剂。