Toxin–antitoxin (TA) systems are genetic modules composed of a toxin interfering with cellular processes and its cognate antitoxin, which counteracts the activity of the toxin. TA modules are widespread in bacterial and archaeal genomes. It has been suggested that TA modules participate in the adaptation of prokaryotes to unfavorable conditions. The Bosea sp. PAMC 26642 used in this study was isolated from the Arctic lichen Stereocaulon sp. There are 12 putative type II TA loci in the genome of Bosea sp. PAMC 26642. Of these, nine functional TA systems have been shown to be toxic in Escherichia coli. The toxin inhibits growth, but this inhibition is reversed when the cognate antitoxin genes are coexpressed, indicating that these putative TA loci were bona fide TA modules. Only the BoVapC1 (AXW83_01405) toxin, a homolog of VapC, showed growth inhibition specific to low temperatures, which was recovered by the coexpression of BoVapB1 (AXW83_01400). Microscopic observation and growth monitoring revealed that the BoVapC1 toxin had bacteriostatic effects on the growth of E. coli and induced morphological changes. Quantitative real time polymerase chain reaction and northern blotting analyses showed that the BoVapC1 toxin had a ribonuclease activity on the initiator tRNA^fMet, implying that degradation of tRNA^fMet might trigger growth arrest in E. coli. Furthermore, the BoVapBC1 system was found to contribute to survival against prolonged exposure at 4°C. This is the first study to identify the function of TA systems in cold adaptation.

中文翻译：

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Bosea sp. 中 VapBC 毒素-抗毒素系统的鉴定和表征。从北极地衣中分离出的 PAMC 26642

毒素-抗毒素 (TA) 系统是遗传模块，由干扰细胞过程的毒素及其同源抗毒素组成，可抵消毒素的活性。TA 模块广泛存在于细菌和古细菌基因组中。有人建议 TA 模块参与原核生物对不利条件的适应。该氧化包西氏菌。本研究中使用的 PAMC 26642 是从北极地衣Stereocaulon sp. 中分离出来的。在Bosea sp的基因组中有 12 个推定的 II 型 TA 基因座。PAMC 26642。其中，九个功能性 TA 系统已被证明对大肠杆菌有毒. 毒素抑制生长，但当同源抗毒素基因共表达时，这种抑制作用被逆转，表明这些推定的 TA 基因座是真正的 TA 模块。只有 BoVapC1 (AXW83_01405) 毒素（VapC 的同系物）显示出对低温具有特异性的生长抑制，这通过 BoVapB1 (AXW83_01400) 的共表达恢复。显微观察和生长监测表明，BoVapC1毒素对大肠杆菌的生长具有抑菌作用并诱导形态变化。定量实时聚合酶链反应和northern印迹分析表明BoVapC1毒素对起始tRNA ^fMet具有核糖核酸酶活性，这意味着tRNA ^fMet的降解可能触发生长停滞大肠杆菌。此外，发现 BoVapBC1 系统有助于在 4°C 下长时间暴露于生存。这是第一项确定 TA 系统在冷适应中的功能的研究。