Yan Qi, Shao Zhihui, Yang Chen, Zhao Guoping
CAS Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences (CAS), Shanghai 200032, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Acta Biochim Biophys Sin (Shanghai). 2025 Jan 23;57(5):738-748. doi: 10.3724/abbs.2024245.
U32 is an industrial strain capable of producing therapeutically useful rifamycin SV. In early days of fermentation studies, nitrate was found to increase the yield of rifamycin along with globally, affecting both carbon and nitrogen metabolism in favor of antibiotic biosynthesis; thus, the (NSE) hypothesis was proposed. Although GlnR is likely the master regulator of the pleotropic effect of NSE, the global metabolism affected by NSE has never been systematically examined. In this study, we use mass spectrometry-based metabolomics to quantitatively monitor the metabolomic responses of . U32 to nitrate supplementation. The concentrations of many metabolites involved in central carbon metabolism, including glucose 6-phosphate, glucose 1-phosphate, UDP-glucose, and acetyl-coenzyme A, decrease significantly after the addition of 80 mM potassium nitrate to the medium. We find that the rifamycin SV production yield could be increased by the addition of glucose during the logarithmic growth phase. Moreover, at multiple time points during glucose supplementation in the mid- and late-exponential phases, the yield of rifamycin SV further increases, reaching 354.3%. Quantitative real-time PCR assays of the key genes corresponding to the synthesis of the rifamycin SV precursor combined with data from metabolomics analysis confirm that carbon source deficiency is compensated for after glucose supplementation and that the expression of genes involved in the pathway of 3-amino-5-hydroxybenzoic acid synthesis by UDP-glucose and glutamine is significantly increased. This preliminary exploration of dynamic metabolomic profiles has the potential to increase our understanding of the NSE.
U32是一种能够产生具有治疗用途的利福霉素SV的工业菌株。在发酵研究的早期，发现硝酸盐能提高利福霉素的产量，同时从全局上影响碳和氮的代谢，有利于抗生素的生物合成；因此，提出了（氮源特异性效应，NSE）假说。尽管GlnR可能是NSE多效性效应的主要调节因子，但受NSE影响的全局代谢从未得到系统研究。在本研究中，我们使用基于质谱的代谢组学方法来定量监测U32对添加硝酸盐的代谢组学响应。向培养基中添加80 mM硝酸钾后，许多参与中心碳代谢的代谢物浓度显著降低，包括6-磷酸葡萄糖、1-磷酸葡萄糖、UDP-葡萄糖和乙酰辅酶A。我们发现，在对数生长期添加葡萄糖可以提高利福霉素SV的产量。此外，在指数中期和后期添加葡萄糖的多个时间点，利福霉素SV的产量进一步增加，达到354.3%。对利福霉素SV前体合成对应的关键基因进行定量实时PCR分析，并结合代谢组学分析数据证实，添加葡萄糖后碳源缺乏得到补偿，UDP-葡萄糖和谷氨酰胺参与3-氨基-5-羟基苯甲酸合成途径的基因表达显著增加。对动态代谢组学图谱的这一初步探索有可能增进我们对NSE的理解。
