Bacterial growth and division require regulated synthesis of the macromolecules used to expand and replicate components of the cell. Transcription of housekeeping genes required for metabolic homeostasis and cell proliferation is guided by the sigma factor σ70. The conserved CarD-like transcriptional regulator, CdnL, associates with promoter regions where σ70 localizes and stabilizes the open promoter complex. However, the contributions of CdnL to metabolic homeostasis and bacterial physiology are not well understood. Here, we show that Caulobacter crescentus cells lacking CdnL have severe morphological and growth defects. Specifically, ΔcdnL cells grow slowly in both rich and defined media, and are wider, more curved, and have shorter stalks than WT cells. These defects arise from transcriptional downregulation of most major classes of biosynthetic genes, leading to significant decreases in the levels of critical metabolites, including pyruvate, α-ketoglutarate, ATP, NAD+, UDP-N-acetyl-glucosamine, lipid II, and purine and pyrimidine precursors. Notably, we find that ΔcdnL cells are glutamate auxotrophs, and ΔcdnL is synthetic lethal with other genetic perturbations that limit glutamate synthesis and lipid II production. Our findings implicate CdnL as a direct and indirect regulator of genes required for metabolic homeostasis that impacts morphogenesis through availability of lipid II and other metabolites.

中文翻译：

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保守的转录调节因子 CdnL 是柄杆菌代谢稳态和形态发生所必需的。

细菌的生长和分裂需要用于扩展和复制细胞成分的大分子的调节合成。代谢稳态和细胞增殖所需的管家基因的转录由西格玛因子 σ70 引导。保守的 CarD 样转录调节因子 CdnL 与 σ70 定位并稳定开放启动子复合体的启动子区域相关。然而，CdnL 对代谢稳态和细菌生理学的贡献尚不清楚。在这里，我们发现缺乏 CdnL 的新月柄杆菌细胞具有严重的形态和生长缺陷。具体而言，ΔcdnL 细胞在丰富培养基和成分确定培养基中生长缓慢，并且比 WT 细胞更宽、更弯曲且茎更短。这些缺陷是由大多数主要生物合成基因的转录下调引起的，导致关键代谢物水平显着降低，包括丙酮酸、α-酮戊二酸、ATP、NAD+、UDP-N-乙酰氨基葡萄糖、脂质 II 和嘌呤和嘧啶前体。值得注意的是，我们发现 ΔcdnL 细胞是谷氨酸营养缺陷型细胞，并且 ΔcdnL 是合成致死细胞，具有限制谷氨酸合成和脂质 II 产生的其他遗传扰动。我们的研究结果表明 CdnL 作为代谢稳态所需基因的直接和间接调节剂，通过脂质 II 和其他代谢物的可用性影响形态发生。