Ma Dongmei, Gu Hanjie, Shi Yanjie, Huang Huiqin, Sun Dongmei, Hu Yonghua
College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing, China.
Institute of Tropical Bioscience and Biotechnology, Hainan Academy of Tropical Agricultural Resource, CATAS, Haikou, China.
Front Microbiol. 2021 Mar 1;12:646299. doi: 10.3389/fmicb.2021.646299. eCollection 2021.
The emergence of drug resistant bacteria is a tricky and confronted problem in modern medicine, and one of important reasons is the widespread of toxin-antitoxin (TA) systems in pathogenic bacteria. (also known as ) is the leading pathogen threatening worldwide fresh and seawater aquaculture industries and has been considered as a model organism for studying intracellular and systemic infections. However, the role of type II TA systems are completely unknown in aquatic pathogenic bacteria. In this study, we identified and characterized a type II TA system, YefM-YoeB, of , where YefM is the antitoxin and YoeB is the toxin. and are co-expressed in a bicistronic operon. When expressed in , YoeB cause bacterial growth arrest, which was restored by the addition of YefM. To investigate the biological role of the TA system, two markerless and in-frame mutant strains, TX01Δ and TX01Δ, were constructed, respectively. Compared to the wild strain TX01, TX01Δ exhibited markedly reduced resistance against oxidative stress and antibiotic, and markedly reduced ability to form persistent bacteria. The deletion of enhanced the bacterial ability of high temperature tolerance, biofilm formation, and host serum resistance, which is the first study about the relationship between type II TA system and serum resistance. infection experiment showed that the inactivation of greatly enhanced bacterial capability of adhesion in host cells. Consistently, experiment suggested that the mutation had an obvious positive effect on bacteria dissemination of fish tissues and general virulence. Introduction of a trans-expressed restored the virulence of TX01Δ. These findings suggest that YefM-YoeB is involved in responding adverse circumstance and pathogenicity of . In addition, we found that YefM-YoeB negatively autoregulated the expression of and YefM could directly bind with own promoter. This study provides first insights into the biological activity of type II TA system YefM-YoeB in aquatic pathogenic bacteria and contributes to understand the pathogenesis of .
耐药细菌的出现是现代医学中一个棘手且面临的问题，重要原因之一是毒素 - 抗毒素（TA）系统在病原菌中广泛存在。（也被称为）是威胁全球淡水和海水养殖业的主要病原菌，并且一直被视为研究细胞内和全身感染的模式生物。然而，II型TA系统在水生病原菌中的作用完全未知。在本研究中，我们鉴定并表征了的一种II型TA系统YefM - YoeB，其中YefM是抗毒素，YoeB是毒素。和在一个双顺反子操纵子中共同表达。当在中表达时，YoeB导致细菌生长停滞，添加YefM可恢复生长。为了研究TA系统的生物学作用，分别构建了两个无标记的和框内突变株TX01Δ和TX01Δ。与野生菌株TX01相比，TX01Δ对氧化应激和抗生素的抗性明显降低，形成持留菌的能力也明显降低。的缺失增强了细菌的耐高温能力、生物膜形成能力和宿主血清抗性，这是关于II型TA系统与血清抗性之间关系的首次研究。感染实验表明，的失活大大增强了细菌在宿主细胞中的粘附能力。同样，实验表明突变对细菌在鱼组织中的传播和总体毒力有明显的积极影响。引入反式表达的可恢复TX01Δ的毒力。这些发现表明YefM - YoeB参与应对的不利环境和致病性。此外，我们发现YefM - YoeB对和的表达进行负向自调控，并且YefM可以直接与自身启动子结合。本研究首次深入了解了水生病原菌中II型TA系统YefM - YoeB的生物学活性，并有助于理解的发病机制。
