Nicastro Gianlucca G, Sibinelli-Sousa Stephanie, Hespanhol Julia Takuno, Santos Thomas W C, Munoz Joseph P, Santos Rosangela S, Perez-Sepulveda Blanca M, Miyamoto Sayuri, Aravind L, de Souza Robson F, Bayer-Santos Ethel
bioRxiv. 2025 May 5:2024.09.27.615498. doi: 10.1101/2024.09.27.615498.
Bacterial warfare is a common and ancient phenomenon in nature, where bacterial species use strategies to inhibit the growth or kill competitors. This involves the production and deployment of antibacterial toxins that disrupt essential cellular processes in target cells. The continuous arms race in which bacteria acquire new toxin and immunity proteins to promote increased adaptation to their environment is responsible for the diversification of this toxin repertoire. Here, we deployed strategies to analyze 10,000 genomes and identify effectors secreted via the type VI secretion system of . We identified 128 candidates, which are widespread in a vast array of serovars and other bacterial species. Tox-Act1 is among the most frequent candidates and was selected for in-depth characterization. Tox-Act1 contains a permuted NlpC/P60 papain-like catalytic core characteristic of lipid-targeting members rather than the typical peptidases or amidases. Evolutionary analysis revealed the relationship of Tox-Act1 with acyltransferases. Biochemical assays with purified toxin and lipidomics of intoxicated cells showed that Tox-Act1 exhibits phospholipase activity, cleaving off acyl groups from phosphatidylglycerol and phosphatidylethanolamine. In addition, we demonstrate that Tox-Act1 is secreted in a T6SS-dependent manner and provide a competitive advantage during colonization of the gut of infected mice. This work broadens our understanding of toxin domains and provides the first direct characterization of a lipid-targeting NlpC/P60 domain in biological conflicts.
细菌战是自然界中一种常见且古老的现象,在这种现象中,细菌物种会采用策略来抑制竞争者的生长或将其杀死。这涉及到抗菌毒素的产生和释放,这些毒素会破坏靶细胞中基本的细胞过程。细菌不断进行军备竞赛,获取新的毒素和免疫蛋白以更好地适应环境,这导致了毒素种类的多样化。在此,我们采用策略分析了10000个基因组,并鉴定了通过VI型分泌系统分泌的效应蛋白。我们鉴定出128个候选蛋白,它们广泛存在于众多血清型及其他细菌物种中。Tox-Act1是最常见的候选蛋白之一,并被选作深入研究的对象。Tox-Act1含有一个重排的NlpC/P60木瓜蛋白酶样催化核心,这是靶向脂质成员的特征,而非典型的肽酶或酰胺酶。进化分析揭示了Tox-Act1与酰基转移酶的关系。对纯化毒素进行的生化分析以及对中毒细胞的脂质组学分析表明,Tox-Act1具有磷脂酶活性,能从磷脂酰甘油和磷脂酰乙醇胺上切割下酰基。此外,我们证明Tox-Act1以T6SS依赖的方式分泌,并在感染小鼠肠道定殖过程中提供竞争优势。这项工作拓宽了我们对毒素结构域的理解,并首次直接表征了生物冲突中靶向脂质的NlpC/P60结构域。