Abstract

Cell proliferation is achieved through numerous enzyme reactions. Temperature governs the activity of each enzyme, ultimately determining the optimal growth temperature. The synthesis of useful chemicals and fuels utilizes a fraction of available metabolic pathways, primarily central metabolic pathways including glycolysis and the tricarboxylic acid cycle. However, it remains unclear whether the optimal temperature for these pathways is correlated with that for cell proliferation. Here, we found that wild-type Corynebacterium glutamicum displayed increased glycolytic activity under non-growing anaerobic conditions at 42.5 °C, at which cells do not proliferate under aerobic conditions. At this temperature, glucose consumption was not inhibited and increased by 28% compared with that at the optimal growth temperature of 30 °C. Transcriptional analysis revealed that a gene encoding glucose transporter (iolT2) was upregulated by 12.3-fold compared with that at 30 °C, with concomitant upregulation of NCgl2954 encoding the iolT2-regulating transcription factor. Deletion of iolT2 decreased glucose consumption rate at 42.5 °C by 28%. Complementation of iolT2 restored glucose consumption rate, highlighting the involvement of iolT2 in the accelerating glucose consumption at an elevated temperature. This study shows that the optimal temperature for glucose metabolism in C. glutamicum under anaerobic conditions differs greatly from that for cell growth under aerobic conditions, being beyond the upper limit of the growth temperature. This is beneficial for fuel and chemical production not only in terms of increasing productivity but also for saving cooling costs.

Key points

• C. glutamicum accelerated anaerobic glucose consumption at elevated temperature.

• The optimal temperature for glucose consumption was above the upper limit for growth.

• Gene expression involved in glucose transport was upregulated at elevated temperature.

Graphical abstract

中文翻译：

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通过在谷氨酸棒杆菌中葡萄糖转运蛋白基因的上调，在不扩散的高温下加速了厌氧葡萄糖的消耗。

摘要

细胞增殖是通过多种酶反应实现的。温度控制着每种酶的活性，最终决定了最佳的生长温度。有用化学物质和燃料的合成利用了一部分可用的代谢途径，主要是包括糖酵解和三羧酸循环在内的主要代谢途径。然而，尚不清楚这些途径的最佳温度是否与细胞增殖的温度相关。在这里，我们发现了野生型谷氨酸棒杆菌在42.5°C的无氧厌氧条件下，糖酵解活性增强，在有氧条件下细胞不会增殖。在此温度下，与最佳生长温度30℃相比，葡萄糖的消耗没有受到抑制，并且增加了28％。转录分析表明，编码基因葡萄糖转运（iolT2）通过上调12.3倍与30相比℃，用伴随上调NCgl2954编码iolT2 -regulating转录因子。删除iolT2可将42.5°C时的葡萄糖消耗率降低28％。补充iolT2可恢复葡萄糖消耗率，突出了iolT2的参与在高温下加速葡萄糖消耗。这项研究表明，厌氧条件下谷氨酸棒杆菌葡萄糖代谢的最佳温度与有氧条件下细胞生长的最佳温度相差很大，超过了生长温度的上限。这不仅对于提高生产率而且对于节省冷却成本都有利于燃料和化学生产。

关键点

•谷氨酸棒杆菌在高温下加速了厌氧葡萄糖的消耗。

•葡萄糖消耗的最佳温度高于生长上限。

•在高温下，涉及葡萄糖转运的基因表达上调。

图形概要