Author summary Pseudomonas syringae is a bacterial plant pathogen that uses a molecular needle; the type 3 injectisome (T3I), to secrete specialised effector proteins into plant cells. Effector secret...

Nature Reviews Microbiology, Published online: 14 November 2025; doi:10.1038/s41579-025-01256-wIn this Review, Basler and colleagues examine the type VI secretion system (T6SS), focusing on the diversity of antibacterial T6SS effectors and the evolutionary forces that shape them. They explain how effectors diversify and highlight interbacterial antagonism as a key driver of this process.

In this Review, Basler and colleagues examine the type VI secretion system (T6SS), focusing on the diversity of antibacterial T6SS effectors and the evolutionary forces that shape them. They explain h...