School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
Appl Microbiol Biotechnol. 2021 May;105(9):3659-3672. doi: 10.1007/s00253-021-11297-9. Epub 2021 Apr 20.
Tetragenococcus halophilus is a moderately halophilic lactic acid bacterium widely used in high-salt food fermentation because of its coping ability under various stress conditions. Bacterial toxin-antitoxin (TA) modules are widely distributed and play important roles in stress response, but those specific for genus Tetragenococcus have never been explored. Here, a bona fide TA module named DinJ-YafQ was characterized in T. halophilus. The toxin protein YafQ acts as a ribonuclease, and its overexpression severely inhibits Escherichia coli growth. These toxic effects can be eliminated by introducing DinJ, indicating that YafQ activity is blocked by the formed DinJ-YafQ complex. In vivo and in vitro assays showed that DinJ alone or DinJ-YafQ complex can repress the transcription of dinJ-yafQ operon by binding directly to the promoter sequence. In addition, dinJ-yafQ is involved in plasmid maintenance and stress response, and its transcriptional level is regulated by various stresses. These findings reveal the possible roles of DinJ-YafQ system in the stress adaptation processes of T. halophilus during fermentation. A single antitoxin DinJ without a cognate toxin protein was also found. Its sequence shows low similarity to that of DinJ, indicating that this antitoxin may have evolved from a different ancestor. Moreover, DinJ can cross-interact with noncognate toxin YafQ and cross-regulate with dinJ-yafQ operon. In summary, DinJ-YafQ characterization may be helpful in investigating the key roles of TA systems in T. halophilus and serves as a foundation for further research. KEY POINTS: • dinJ-yafQ is the first functional TA module characterized in T. halophilus and upregulated significantly upon osmotic and acidic stress. • DinJ can exhibit physical and transcriptional interplay with DinJ-YafQ. • dinJ may be acquired from bacteria in distant affiliation and inserted into the T. halophilus genome through horizontal gene transfer.
盐单胞菌是一种中度嗜盐乳酸菌，由于其在各种应激条件下的适应能力，被广泛应用于高盐食品发酵。细菌毒素-抗毒素（TA）模块广泛分布，在应激反应中发挥重要作用，但从未探索过特定于四球菌属的 TA 模块。在这里，我们在盐单胞菌中鉴定了一个真正的 TA 模块 DinJ-YafQ。毒素蛋白 YafQ 作为一种核糖核酸酶，其过表达严重抑制大肠杆菌的生长。通过引入 DinJ，可以消除这些毒性作用，表明 YafQ 活性被形成的 DinJ-YafQ 复合物所阻断。体内和体外实验表明，DinJ 单独或 DinJ-YafQ 复合物可以通过直接结合启动子序列来抑制 dinJ-yafQ 操纵子的转录。此外，dinJ-yafQ 参与质粒维持和应激反应，其转录水平受到各种应激的调节。这些发现揭示了 DinJ-YafQ 系统在发酵过程中盐单胞菌适应应激的可能作用。还发现了一个没有同源毒素蛋白的单一抗毒素 DinJ。其序列与 DinJ 的序列相似性较低，表明该抗毒素可能来自不同的祖先。此外，DinJ 可以与非同源毒素 YafQ 发生交叉相互作用，并与 dinJ-yafQ 操纵子发生交叉调控。总之，DinJ-YafQ 的鉴定可能有助于研究 TA 系统在盐单胞菌中的关键作用，并为进一步的研究奠定基础。 关键点： • dinJ-yafQ 是第一个在盐单胞菌中被鉴定的功能性 TA 模块，在渗透和酸性应激下显著上调。 • DinJ 可以与 DinJ-YafQ 发生物理和转录相互作用。 • dinJ 可能来自远缘细菌，并通过水平基因转移插入盐单胞菌基因组。
