Song Sooyeon, Wood Thomas K
Department of Animal Science, Jeonbuk National University, Jeonju-si, South Korea.
Department of Chemical Engineering, Pennsylvania State University, University Park, PA, United States.
Front Microbiol. 2020 Aug 13;11:1895. doi: 10.3389/fmicb.2020.01895. eCollection 2020.
Toxin/antitoxin (TA) systems are present in most prokaryote genomes. Toxins are almost exclusively proteins that reduce metabolism (but do not cause cell death), and antitoxins are either RNA or proteins that counteract the toxin or the RNA that encodes it. Although TA systems clearly stabilize mobile genetic elements, after four decades of research, the physiological roles of chromosomal TA systems are less clear. For example, recent reports have challenged the notion of TA systems as stress-response elements, including a role in creating the dormant state known as persistence. Here, we present evidence that a primary physiological role of chromosomally encoded TA systems is phage inhibition, a role that is also played by some plasmid-based TA systems. This includes results that show some CRISPR-Cas system elements are derived from TA systems and that some CRISPR-Cas systems mimic the host growth inhibition invoked by TA systems to inhibit phage propagation.
毒素/抗毒素（TA）系统存在于大多数原核生物基因组中。毒素几乎都是降低新陈代谢（但不导致细胞死亡）的蛋白质，而抗毒素则是抵消毒素或其编码RNA的RNA或蛋白质。尽管TA系统显然稳定了可移动遗传元件，但经过四十年的研究，染色体TA系统的生理作用仍不太清楚。例如，最近的报告对TA系统作为应激反应元件的概念提出了挑战，包括在形成称为持续状态的休眠状态中的作用。在这里，我们提供证据表明，染色体编码的TA系统的主要生理作用是噬菌体抑制，一些基于质粒的TA系统也发挥这一作用。这包括一些结果，表明一些CRISPR-Cas系统元件源自TA系统，并且一些CRISPR-Cas系统模拟TA系统引起的宿主生长抑制以抑制噬菌体繁殖。
