Studies on a Widely Distributed Phage Tail-Derived Toxin Injection System

感染细菌的病毒（噬菌体或噬菌体）是地球上最丰富的生物实体。大多数的蜥蜴都有一个二十面体的头部，头部包含双链DNA基因组，头部的一个顶点上有一条“尾巴”。尾巴负责附着在宿主细菌上，并将基因组传递到细胞内部。因此，噬菌体尾部是非常复杂的纳米机器，能够特异性地结合细菌的外表面，穿透细胞壁和细胞膜，并将大分子（DNA和蛋白质）注入细胞质中。噬菌体尾作为大分子注射装置的巨大有效性已经导致它们被细菌出于各种目的而吸收，如VI型分泌系统所例示的，其是多种革兰氏阴性生物体中广泛存在的噬菌体尾衍生的毒力决定子。

The viruses that infect bacteria (bacteriophages or phages) are the most abundant biological entities on earth. Most phages possess an icosahedral head containing their double-stranded DNA genome and a “tail” attached to one vertex of the head. The tail is responsible for attaching to the host bacterium and delivering the genome to the interior of the cell. As such, phage tails are very complex nanomachines with the ability to specifically bind the outer surface of bacteria, penetrate the cell wall and membranes, and inject macromolecules (DNA and proteins) into the cytoplasm. The tremendous effectiveness of phage tails as macromolecular injection devices has led to their being co-opted by bacteria for a variety of purposes, as exemplified by the Type VI secretion system, which is a widespread phage tail-derived virulence determinant in diverse Gram-negative organisms.