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两种防御系统消除第七次大流行的霍乱弧菌质粒
2022-04-10 16:07
来源：小柯机器人

近日，瑞士洛桑联邦理工学院Melanie Blokesch、David W. Adams等研究人员合作发现，两种防御系统消除第七次大流行的霍乱弧菌质粒。这一研究成果于2022年4月6日在线发表在国际学术期刊《自然》上。

研究人员确定了霍乱弧菌El Tor菌株中保守的两个质粒防御系统，这些菌株导致了正在进行的第七次霍乱大流行。这些系统被称为DdmABC和DdmDE，在两个主要的致病岛上编码，是目前大流行菌株的一个标志。结果表明，这些模块合作通过降解迅速消除小型多拷贝质粒。此外，DdmABC系统是广泛存在的，可以通过触发细胞自杀（中止性感染，或Abi）来抵御噬菌体感染。
 
值得注意的是，研究人员继续发现，通过一个类似Abi的机制，DdmABC增加了大型低拷贝数质粒的负担，包括一个广泛的宿主IncC多药抗性质粒，这创造了一个适应性劣势，对携带质粒的细胞进行反向选择。这些研究结果回答了一个长期存在的问题：为什么质粒虽然在环境菌株中很丰富，但在大流行菌株中却很罕见；对理解抗生素抗性质粒的传播有意义；并对两种防御系统之间的相互作用如何形成大流行性霍乱中最成功品系的演化提供了见解。
 
据悉，水平基因转移可以引发细菌进化的快速转变。在各种移动遗传因子（特别是噬菌体和质粒）的驱动下，在物种内和物种间分享基因的能力是细菌的特殊适应性的基础。然而，入侵性的移动遗传元素也会给宿主带来严重的风险；因此，细菌已经进化出大量的防御措施来对付这些元件。
 
附：英文原文
 
Title: Two defence systems eliminate plasmids from seventh pandemic Vibrio cholerae

Author: Jasklska, Milena, Adams, David W., Blokesch, Melanie

Issue&Volume: 2022-04-06

Abstract: Horizontal gene transfer can trigger rapid shifts in bacterial evolution. Driven by a variety of mobile genetic elements—in particular bacteriophages and plasmids—the ability to share genes within and across species underpins the exceptional adaptability of bacteria. Nevertheless, invasive mobile genetic elements can also present grave risks to the host; bacteria have therefore evolved a vast array of defences against these elements1. Here we identify two plasmid defence systems conserved in the Vibrio cholerae El Tor strains responsible for the ongoing seventh cholera pandemic2,3,4. These systems, termed DdmABC and DdmDE, are encoded on two major pathogenicity islands that are a hallmark of current pandemic strains. We show that the modules cooperate to rapidly eliminate small multicopy plasmids by degradation. Moreover, the DdmABC system is widespread and can defend against bacteriophage infection by triggering cell suicide (abortive infection, or Abi). Notably, we go on to show that, through an Abi-like mechanism, DdmABC increases the burden of large low-copy-number conjugative plasmids, including a broad-host IncC multidrug resistance plasmid, which creates a fitness disadvantage that counterselects against plasmid-carrying cells. Our results answer the long-standing question of why plasmids, although abundant in environmental strains, are rare in pandemic strains; have implications for understanding the dissemination of antibiotic resistance plasmids; and provide insights into how the interplay between two defence systems has shaped the evolution of the most successful lineage of pandemic V. cholerae.

DOI: 10.1038/s41586-022-04546-y

Source: https://www.nature.com/articles/s41586-022-04546-y

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
投稿链接：http://www.nature.com/authors/submit_manuscript.html


本期文章：《自然》：Online/在线发表

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