Maintenance of the Shigella sonnei Virulence Plasmid Is Dependent on Its Repertoire and Amino Acid Sequence of Toxin-Antitoxin Systems.
Maintenance of the Shigella sonnei Virulence Plasmid Is Dependent on Its Repertoire and Amino Acid Sequence of Toxin-Antitoxin Systems.
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DOI：
10.1128/jb.00519-21
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发表时间：
2022-03-15
影响因子：
3.2
通讯作者：
Tang CM
中科院分区：
文献类型：
--
作者：
Martyn JE;Pilla G;Hollingshead S;Winther KS;Lea S;McVicker G;Tang CM
宋内氏志贺氏菌是细菌性痢疾的主要原因，由于多重耐药的传播，人们越来越关注它。宋内氏链球菌含有pINV，这是一个编码III型分泌系统(T3SS)的∼210 kb质粒，而T3SS是毒力所必需的。在实验室的生长过程中，宋内氏链球菌会在高频下自发产生毒力，这阻碍了对这种重要病原体的研究和疫苗的开发。在这里，我们研究了宋内氏链球菌产生无毒的分子基础，发现无毒主要是由pINV缺失造成的，这与以前的发现是一致的。祖先的缺失已经导致宋内氏志贺菌pINV中两个与质粒维持有关的毒素-抗毒素(TA)系统CcdAB和GMVAT的丢失，这两个系统存在于福氏志贺菌的pINV上。我们发现，这些TA系统的引入减少了pINV的丢失，但并没有消除pINV的丢失，而与福氏志贺氏菌VapBC相比，在S.sonnei VapBC TA系统中发现的单一氨基酸多态性也是导致pINV丢失的原因之一。无毒力还源于pINV中T3SS相关基因的缺失，即插入序列(ISS)之间的重组。由于ISS的分布和谱系不同，这些事件与在福氏志贺氏菌中观察到的事件不同。我们的研究结果表明，TA系统和ISS影响宋内氏葡萄球菌的质粒动力学和丢失，可用于疫苗的设计和评价。宋内氏志贺氏菌是高收入和工业化国家志贺氏菌病的主要原因，是一种新出现的多重耐药病原体。研究这种细菌的一个重大挑战是，在实验室的生长过程中，它会通过失去毒力质粒(PINV)而自发变得无毒。在这里，我们破译了导致宋内氏志贺氏菌无毒的机制，以及与福氏志贺氏菌相比，质粒编码的毒素-抗毒素(TA)系统的有限酶谱和氨基酸序列如何使pINV在该细菌中的维持效率较低。我们的发现突出表明，在近缘物种中，质粒之间的细微差异具有显著的影响，可以被利用来减少宋内氏链霉菌中的质粒丢失。这应该会促进对这种细菌的研究和疫苗的开发。
Shigella sonnei is a major cause of bacillary dysentery and an increasing concern due to the spread of multidrug resistance. S. sonnei harbors pINV, an ∼210 kb plasmid that encodes a type III secretion system (T3SS), which is essential for virulence. During growth in the laboratory, avirulence arises spontaneously in S. sonnei at high frequency, hampering studies on and vaccine development against this important pathogen. Here, we investigated the molecular basis for the emergence of avirulence in S. sonnei and showed that avirulence mainly results from pINV loss, which is consistent with previous findings. Ancestral deletions have led to the loss from S. sonnei pINV of two toxin-antitoxin (TA) systems involved in plasmid maintenance, CcdAB and GmvAT, which are found on pINV in Shigella flexneri. We showed that the introduction of these TA systems into S. sonnei pINV reduced but did not eliminate pINV loss, while the single amino acid polymorphisms found in the S. sonnei VapBC TA system compared with S. flexneri VapBC also contributed to pINV loss. Avirulence also resulted from deletions of T3SS-associated genes in pINV through recombination between insertion sequences (ISs) on the plasmid. These events differed from those observed in S. flexneri due to the different distribution and repertoire of ISs. Our findings demonstrated that TA systems and ISs influenced plasmid dynamics and loss in S. sonnei and could be exploited for the design and evaluation of vaccines. IMPORTANCE Shigella sonnei is the major cause of shigellosis in high-income and industrializing countries and is an emerging, multidrug-resistant pathogen. A significant challenge when studying this bacterium is that it spontaneously becomes avirulent during growth in the laboratory through loss of its virulence plasmid (pINV). Here, we deciphered the mechanisms leading to avirulence in S. sonnei and how the limited repertoire and amino acid sequences of plasmid-encoded toxin-antitoxin (TA) systems make the maintenance of pINV in this bacterium less efficient compared with Shigella flexneri. Our findings highlighted how subtle differences in plasmids in closely related species have marked effects and could be exploited to reduce plasmid loss in S. sonnei. This should facilitate research on this bacterium and vaccine development.