Department of Microbiology, University of Washington, Seattle, Washington 98195, USA.
Nature. 2011 Jul 20;475(7356):343-7. doi: 10.1038/nature10244.
Peptidoglycan is the major structural constituent of the bacterial cell wall, forming a meshwork outside the cytoplasmic membrane that maintains cell shape and prevents lysis. In Gram-negative bacteria, peptidoglycan is located in the periplasm, where it is protected from exogenous lytic enzymes by the outer membrane. Here we show that the type VI secretion system of Pseudomonas aeruginosa breaches this barrier to deliver two effector proteins, Tse1 and Tse3, to the periplasm of recipient cells. In this compartment, the effectors hydrolyse peptidoglycan, thereby providing a fitness advantage for P. aeruginosa cells in competition with other bacteria. To protect itself from lysis by Tse1 and Tse3, P. aeruginosa uses specific periplasmically localized immunity proteins. The requirement for these immunity proteins depends on intercellular self-intoxication through an active type VI secretion system, indicating a mechanism for export whereby effectors do not access donor cell periplasm in transit.
肽聚糖是细菌细胞壁的主要结构成分，形成细胞质膜外的网格结构，维持细胞形状并防止裂解。在革兰氏阴性菌中，肽聚糖位于周质空间，由外膜保护免受外源溶酶的作用。在这里，我们表明铜绿假单胞菌的 VI 型分泌系统突破了这一障碍，将两种效应蛋白 Tse1 和 Tse3 递送到受体细胞的周质空间。在这个隔室中，效应物水解肽聚糖，从而为铜绿假单胞菌细胞在与其他细菌的竞争中提供了适应性优势。为了防止自身被 Tse1 和 Tse3 裂解，铜绿假单胞菌使用特定的周质局部免疫蛋白。这些免疫蛋白的需求取决于通过主动 VI 型分泌系统的细胞间自我中毒，表明了一种通过效应物在运输过程中不进入供体细胞周质的出口机制。
