State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
College of Life Sciences, Tarim University, Alar, Xinjiang, China.
Microbiol Spectr. 2024 Jun 4;12(6):e0427823. doi: 10.1128/spectrum.04278-23. Epub 2024 May 7.
Within the realm of Gram-negative bacteria, bacteriocins are secreted almost everywhere, and the most representative are colicin and pyocin, which are secreted by and , respectively. Signal peptides at the amino terminus of bacteriocins or ABC transporters can secrete bacteriocins, which then enter bacteria through cell membrane receptors and exert toxicity. In general, the bactericidal spectrum is usually narrow, killing only the kin or closely related species. Our previous research indicates that YPK_0952 is an effector of the third Type VI secretion system (T6SS-3) in . Next, we sought to determine its identity and characterize its toxicity. We found that YPK_0952 (a pyocin-like effector) can achieve intra-species and inter-species competitive advantages through both contact-dependent and contact-independent mechanisms mediated by the T6SS-3 while enhancing the intestinal colonization capacity of . We further identified YPK_0952 as a DNase dependent on Mg, Ni, Mn, and Co bivalent metal ions, and the homologous immune protein YPK_0953 can inhibit its activity. In summary, YPK_0952 exerts toxicity by degrading nucleic acids from competing cells, and YPK_0953 prevents self-attack in .IMPORTANCEBacteriocins secreted by Gram-negative bacteria generally enter cells through specific interactions on the cell surface, resulting in a narrow bactericidal spectrum. First, we identified a new pyocin-like effector protein, YPK_0952, in the third Type VI secretion system (T6SS-3) of . YPK_0952 is secreted by T6SS-3 and can exert DNase activity through contact-dependent and contact-independent entry into nearby cells of the same and other species (e.g., ) to help to exert a competitive advantage and promote intestinal colonization. This discovery lays the foundation for an in-depth study of the different effector protein types within the T6SS and their complexity in competing interactions. At the same time, this study provides a new development for the toolbox of toxin/immune pairs for studying Gram-negative bacteriocin translocation.
在革兰氏阴性菌中，细菌素几乎无处不在分泌，其中最具代表性的是 colicin 和 pyocin，分别由 和 分泌。细菌素或 ABC 转运蛋白氨基末端的信号肽可以分泌细菌素，然后通过细胞膜受体进入细菌并发挥毒性。一般来说，杀菌谱通常较窄，只杀死亲缘或密切相关的物种。我们之前的研究表明，YPK_0952 是 的第三型 VI 分泌系统 (T6SS-3) 的效应物。接下来，我们试图确定其身份并表征其毒性。我们发现，YPK_0952（一种类似噬菌体的效应物）可以通过 T6SS-3 介导的接触依赖和非接触依赖机制在种内和种间竞争中获得优势，同时增强 的肠道定植能力。我们进一步鉴定出 YPK_0952 是一种依赖 Mg、Ni、Mn 和 Co 二价金属离子的 DNase，同源免疫蛋白 YPK_0953 可以抑制其活性。总之，YPK_0952 通过降解竞争细胞的核酸发挥毒性，YPK_0953 可防止 在 中自我攻击。
重要性：革兰氏阴性菌分泌的细菌素通常通过细胞表面的特定相互作用进入细胞，导致杀菌谱较窄。首先，我们在 的第三型 VI 分泌系统 (T6SS-3) 中鉴定出一种新的类似噬菌体的效应蛋白 YPK_0952。YPK_0952 由 T6SS-3 分泌，可通过接触依赖和非接触依赖的方式进入同种和其他物种（如 ）的邻近细胞，发挥 DNase 活性，帮助 发挥竞争优势并促进肠道定植。这一发现为深入研究 T6SS 中的不同效应蛋白类型及其在竞争相互作用中的复杂性奠定了基础。同时，本研究为研究革兰氏阴性细菌素转运的毒素/免疫对提供了一种新的工具。
