The type VI secretion system (T6SS) is a transmembrane multiprotein nanomachine employed by many Gram-negative bacterial species to translocate, in a contact-dependent manner, effector proteins into adjacent prokaryotic or eukaryotic cells. Typically, the T6SS gene cluster encodes at least 13 conserved core components for the apparatus assembly and other less conserved accessory proteins and effectors. It functions as a contractile tail machine comprising a TssB/C sheath and an expelled puncturing device consisting of an Hcp tube topped by a spike complex of VgrG and PAAR proteins. Contraction of the sheath propels the tube out of the bacterial cell into a target cell and leads to the injection of toxic proteins. Different bacteria use the T6SS for specific roles according to the niche and versatility of the organism. Effectors are present both as cargo (by non-covalent interactions with one of the core components) or specialized domains (fused to structural components). Although several anti-prokaryotic effectors T6SSs have been studied, recent studies have led to a substantial increase in the number of characterized anti-eukaryotic effectors. Against eukaryotic cells, the T6SS is involved in modifying and manipulating diverse cellular processes that allows bacteria to colonize, survive and disseminate, including adhesion modification, stimulating internalization, cytoskeletal rearrangements and evasion of host innate immune responses.

VI 型分泌系统 (T6SS) 是一种跨膜多蛋白纳米机器，被许多革兰氏阴性细菌物种采用，以接触依赖性方式将效应蛋白易位到相邻的原核或真核细胞中。通常，T6SS 基因簇编码至少 13 个用于装置组装的保守核心组件以及其他不太保守的辅助蛋白和效应子。它起到收缩尾部机器的作用，包括 TssB/C 鞘和排出穿刺装置，该穿刺装置由 Hcp 管组成，顶部有 VgrG 和 PAAR 蛋白的尖峰复合物。鞘的收缩将管子从细菌细胞中推出到靶细胞中，并导致有毒蛋白质的注射。根据生物体的生态位和多功能性，不同的细菌使用 T6SS 发挥特定的作用。效应器既可以作为货物（通过与核心成分之一的非共价相互作用）也可以作为特殊域（与结构成分融合）存在。尽管已经研究了几种抗原核效应子T6SS，但最近的研究导致特征性抗真核效应子的数量大幅增加。针对真核细胞，T6SS 参与修改和操纵多种细胞过程，使细菌能够定植、生存和传播，包括粘附修饰、刺激内化、细胞骨架重排和逃避宿主先天免疫反应。