Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, PO Box 6888, Tianjin, 300072, People's Republic of China,
J Ind Microbiol Biotechnol. 2013 Nov;40(11):1303-14. doi: 10.1007/s10295-013-1326-y. Epub 2013 Aug 29.
The addition of precursors was one strategy to improve antibiotic production. The exogenous proline and glutamate, as precursors of streptolydigin, could significantly improve the streptolydigin production, but their underlying molecular mechanisms remain unknown. Herein, metabolomic analysis was carried out to explore the metabolic responses of Streptomyces lydicus to the additions of proline and glutamine. The significant differences in the quantified 53 metabolites after adding the exogenous proline and glutamate were enunciated by gas chromatography coupled to time-of-flight mass spectrometry. Among them, the levels of some fatty acids (e.g., dodecanoic acid, octadecanoic acid, hexadecanoic acid) were significantly decreased after adding glutamate and proline, indicating that the inhibition of fatty acid synthesis might be benefit for the accumulation of streptolydigin. Particularly, the dramatic changes of the identified metabolites, which are involved in glycolysis, the tricarboxylic acid cycle, and the amino acid and fatty acid metabolism, revealed that the additions of glutamate and proline possibly caused the metabolic cross-talk in S. lydicus. Additionally, the level of intracellular glutamate dramatically enhanced at 12 h after adding proline, showing that exogenous proline may be firstly convert into glutamate and consequently result in crease of the streptolydigin production. The high levels of streptolydigin at 12 and 24 h after adding glutamate unveiled that part glutamate were rapidly used to synthesize the streptolydigin. Furthermore, there is the significant difference in metabolomic characteristics of S. lydicus after adding glutamate and proline, uncovering that multiple regulatory pathways are involved in responses to the additions of exogenous glutamate and proline. Taken together, exogenous glutamate and proline not only directly provided the precursors of streptolydigin biosynthesis, but also might alter the metabolic homeostasis of S. lydicus E9 during improving the production of streptolydigin.
添加前体是提高抗生素产量的一种策略。脯氨酸和谷氨酸作为链雷素的前体，可以显著提高链雷素的产量，但它们的潜在分子机制尚不清楚。在此，我们进行了代谢组学分析，以探讨链霉菌对添加脯氨酸和谷氨酸的代谢反应。气相色谱-飞行时间质谱联用定量分析了添加脯氨酸和谷氨酸后 53 种代谢物的显著差异。其中，添加谷氨酸和脯氨酸后，一些脂肪酸（如十二烷酸、十八烷酸、十六烷酸）的水平显著降低，表明抑制脂肪酸合成可能有利于链雷素的积累。特别是，所鉴定的代谢物发生了剧烈变化，这些代谢物涉及糖酵解、三羧酸循环以及氨基酸和脂肪酸代谢，这表明谷氨酸和脯氨酸的添加可能导致链霉菌中的代谢交叉。此外，添加脯氨酸 12 小时后，细胞内谷氨酸的水平显著升高，表明外源性脯氨酸可能首先转化为谷氨酸，从而导致链雷素产量的增加。添加谷氨酸 12 和 24 小时后链雷素的高产量表明，部分谷氨酸被迅速用于合成链雷素。此外，添加谷氨酸和脯氨酸后链霉菌的代谢组学特征存在显著差异，表明参与对外源谷氨酸和脯氨酸添加反应的调控途径有多种。总之，外源性谷氨酸和脯氨酸不仅直接提供了链雷素生物合成的前体，而且可能在提高链雷素产量的过程中改变链霉菌 E9 的代谢平衡。
