How to kill your rivals: microbial warfare mediated by the Type VI secretion system
Microbial organisms do not typically exist in isolation or as single populations, rather they exist as mixed microbial communities whose members interact co-operatively or competitively by a variety of mechanisms. The Type VI secretion system (T6SS) is widespread in Gram-negative bacteria and represents a contractile nano-machine that can fire toxic effector proteins directly into neighbouring cells. The primary role if the T6SS appears to be to deliver anti-bacterial effector proteins into rival bacterial cells as a means of inter-bacterial competition. Here, I will describe how the opportunistic pathogen, Serratia marcescens, deploys its potent anti-bacterial T6SS to achieve such efficient bacterial killing and the exciting new observation that this system can also deliver anti-fungal effectors to attack fungal competitors.