School of Life Science and Technology, Tokyo Institute of Technology, 4250 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8501, Japan.
Appl Microbiol Biotechnol. 2021 Sep;105(18):6909-6920. doi: 10.1007/s00253-021-11516-3. Epub 2021 Aug 31.
From the previous transcriptome analysis (Hirasawa et al. Biotechnol J 13:e1700612, 2018), it was found that expression of genes whose expression is regulated by stress-responsive transcriptional regulators was altered during penicillin-induced glutamic acid production in Corynebacterium glutamicum. Therefore, we investigated whether stress treatments, such as copper and iron addition, could induce glutamic acid production in C. glutamicum and found that the addition of copper did induce glutamic acid production in this species. Moreover, we also determined that glutamic acid production levels upon copper addition in a gain-of-function mutant strain of the mechanosensitive channel, NCgl1221, involved in glutamic acid export, were comparable to glutamic acid levels produced upon penicillin addition and biotin limitation in the wild-type strain. Furthermore, disruption of the odhI gene, which encodes a protein responsible for the decreased activity of the 2-oxoglutarate dehydrogenase complex during glutamic acid production, significantly diminished glutamic acid production induced by copper. These results indicate that copper can induce glutamic acid production and this induction requires OdhI like biotin limitation and penicillin addition, but a gain-of-function mutation in the NCgl1221 mechanosensitive channel is necessary for its high-level glutamic acid production. However, a significant increase in odhI transcription was not observed with copper addition in both wild-type and NCgl1221 gain-of-function mutant strains. In addition, disruption of the csoR gene encoding a copper-responsive transcriptional repressor enhanced copper-induced glutamic acid production in the NCgl1221 gain-of-function mutant, indicating that unidentified CsoR-regulated genes may contribute to copper-induced glutamic acid production in C. glutamicum. KEY POINTS: • Copper can induce glutamic acid production by Corynebacterium glutamicum. • Copper-induced glutamic acid production requires OdhI protein. • Copper-induced glutamic acid production requires a gain-of-function mutation in the mechanosensitive channel NCgl1221, which is responsible for the production of glutamic acid.
从之前的转录组分析（Hirasawa 等人，生物技术杂志 13:e1700612, 2018）中发现，在谷氨酸棒杆菌的青霉素诱导谷氨酸生产过程中，受应激反应转录调节剂调控的基因表达发生了改变。因此，我们研究了应激处理（如添加铜和铁）是否能诱导谷氨酸棒杆菌产生谷氨酸，发现添加铜确实能诱导该物种产生谷氨酸。此外，我们还确定，在机械敏感通道 NCgl1221 的功能获得突变株中添加铜诱导的谷氨酸产量与野生型菌株中添加青霉素和生物素限制时产生的谷氨酸水平相当。此外，破坏编码在谷氨酸生产过程中降低 2-氧戊二酸脱氢酶复合物活性的 OdhI 基因的活性，显著降低了铜诱导的谷氨酸产量。这些结果表明，铜可以诱导谷氨酸的产生，这种诱导作用类似于生物素限制和青霉素添加，但 NCgl1221 机械敏感通道的功能获得性突变是其高产谷氨酸所必需的。然而，在野生型和 NCgl1221 功能获得性突变株中，添加铜时并未观察到 OdhI 基因转录的显著增加。此外，破坏编码铜反应性转录抑制剂的 csoR 基因，增强了 NCgl1221 功能获得性突变株中铜诱导的谷氨酸产生，表明未鉴定的 CsoR 调控基因可能有助于铜诱导谷氨酸棒杆菌产生谷氨酸。关键点：• 铜可以诱导谷氨酸棒杆菌产生谷氨酸。• 铜诱导的谷氨酸生产需要 OdhI 蛋白。• 铜诱导的谷氨酸生产需要机械敏感通道 NCgl1221 的功能获得性突变，该通道负责谷氨酸的产生。
