Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
Department of Biochemistry and Molecular Biology, Center for Advanced Biotechnology and Medicine, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey, USA.
Appl Environ Microbiol. 2019 Oct 1;85(20). doi: 10.1128/AEM.00915-19. Print 2019 Oct 15.
Toxin-antitoxin (TA) systems consist of toxin-inhibiting diverse cellular functions (e.g., DNA replication, transcription, and translation) and a noncoding RNA or protein antitoxin. TA systems are associated with various cellular events, such as stress responses, programmed cell death, and bacterial pathogenicity. Recent advances in genome sequencing and bioinformatics research have demonstrated that most bacteria harbor various kinds of TA modules on their chromosomes; however, there is little understanding of chromosomally encoded TA systems in the Gram-positive pathogen Here, we report on newly discovered TA systems, each of which is composed of two proteins. Manual search and gene operon prediction analysis identified eight 2-gene operons as potential candidates for TA systems. Subsequently, using an host killing and rescue assay, we demonstrated that four of the eight candidates worked as TA systems, designated , , , and Moreover, the TsaT, TsbT, TscT, and TsdT toxins inhibited growth, and the toxicity of TsbT was neutralized by coexpressing the gene in the native host, Further, the bioinformatics analysis of the gene clusters revealed that TsaAT, TsbAT, TscAT, and TsdAT did not exhibit sequence similarity to known bacterial TA systems, and their homologues were present only within species and not among any other bacteria. Our results further advance not only the understanding of TA systems but also the study of unannotated TA systems in various bacterial species. Recent advances in genome sequencing and bioinformatics research have demonstrated that most pathogenic bacteria harbor a large number of chromosomally encoded toxin-antitoxin (TA) modules. However, little is known about the TA systems in Here, we newly identified four TA systems using a combination of manual base-by-base screening and functional analysis in Moreover, all toxins of the identified TA systems caused growth inhibition in the native host Although the newly identified TA systems did not exhibit sequence similarity with known bacterial TA systems, their orthologues were conserved only among other species, indicating their uniqueness to staphylococci. Our approach opens the possibility for studying unannotated TA systems in various bacterial species.
毒素-抗毒素 (TA) 系统由抑制多种细胞功能（如 DNA 复制、转录和翻译）的毒素和非编码 RNA 或蛋白质抗毒素组成。TA 系统与各种细胞事件相关，如应激反应、程序性细胞死亡和细菌致病性。基因组测序和生物信息学研究的最新进展表明，大多数细菌在其染色体上都拥有各种 TA 模块；然而，对于革兰氏阳性病原体中的染色体编码 TA 系统，人们的了解甚少。在这里，我们报告了新发现的 TA 系统，每个系统都由两种蛋白质组成。手动搜索和基因操纵子预测分析鉴定了 8 个 2 基因操纵子作为 TA 系统的潜在候选者。随后，使用 宿主杀伤和拯救测定，我们证明了这 8 个候选者中的 4 个作为 TA 系统起作用，分别命名为 、 、 和 。此外，TsaT、TsbT、TscT 和 TsdT 毒素抑制 生长，并且在天然宿主中表达 基因可以中和 TsbT 的毒性。进一步，基因簇的生物信息学分析表明，TsaAT、TsbAT、TscAT 和 TsdAT 与已知的细菌 TA 系统没有序列相似性，它们的同源物仅存在于 种内，而不在任何其他细菌中存在。我们的研究结果不仅进一步提高了对 TA 系统的理解，而且还提高了对各种细菌中未注释的 TA 系统的研究。基因组测序和生物信息学研究的最新进展表明，大多数致病性细菌都拥有大量染色体编码的毒素-抗毒素（TA）模块。然而，对于 中的 TA 系统知之甚少。在这里，我们使用 中的手动逐个碱基筛选和功能分析相结合的方法新鉴定了 4 个 TA 系统。此外，所鉴定的 TA 系统的所有毒素在天然宿主中都引起生长抑制。虽然新鉴定的 TA 系统与已知的细菌 TA 系统没有序列相似性，但它们的同源物仅在其他 种内保守，这表明它们对葡萄球菌具有独特性。我们的方法为研究各种细菌中的未注释的 TA 系统开辟了可能性。
