革兰氏阴性菌Ⅵ型分泌系统及其参与金属离子转运的研究进展

Advances of the Gram-negative bacterial type Ⅵ secretion system and its function for metal ion acquisition

摘要:

细菌通过其分泌系统将特定的效应蛋白输送到外界环境或进入靶细胞中，从而在细菌和宿主、细菌和微生物群落的相互作用中占据适应性优势。Ⅵ型分泌系统（The type VI secretion system，T6SS）是革兰氏阴性菌中广泛存在的大分子分泌装置，其结构和功能类似于可收缩的噬菌体尾针样，通过细胞间直接接触将细菌各种酶或毒素效应蛋白转运到原核和真核生物中，从而介导细菌间竞争以及对宿主的致病过程。有些效应蛋白还可通过非接触依赖的方式进入胞外环境来帮助细菌获取稀缺金属离子，并且它们对应激条件下细胞内金属稳态的维持至关重要。这篇综述总结了Ⅵ型分泌系统的结构、组装及其分泌的效应蛋白，并重点阐述了Ⅵ型分泌系统在多种金属离子转运机制中作用的研究进展，有助于理解T6SS在细菌间相互作用和细菌感染过程中发挥的重要作用。

关键词:Ⅵ型分泌系统;效应蛋白;细菌间竞争;致病性;金属转运

Abstract:

Bacterial secretion systems can deliver specific effector molecular to outer environment or directly into target cells, resulting in the adaptive advantage from interaction between bacteria and host or bacteria in microbial communities. The type Ⅵ secretion system (T6SS) is a macromolecular secretory apparatus which is functionally and structurally analogous to the needle-like contractile tail of bacteriophages, wide-spreading in Gram-negative bacteria. It can translocate diverse enzyme and toxins of bacteria into eukaryotic or prokaryotic target cells in a contact-dependent manner. After delivery, the effector proteins can make an impact on both interbacterial competition and pathogenicity. In addition, some effectors can also enter the extracellular milieu in a non-contact dependent manner to help bacteria obtain scarce metal ions, which is essential for the maintenance of intracellular metal homeostasis under stress conditions. In this review, we summarize the advances in understanding the relevant aspects from the structure and assembly to the function of T6SS. We also focus on the broad area of T6SS effector and its mechanism of metal ion translocation, which contributes to our comprehension of the crucial role of T6SS in the microbial competition and host infection.

Key words:type Ⅵ secretion system;effector proteins;interbacterial competition;pathogenicity;metal ion acquisition