image: Translocated LqqE1 impairs K1-T6SS function by directly binding to VgrG1 of P. putida.
Credit: ©Science China Press
Interspecies competition plays a crucial role in shaping microbial community dynamics and influencing host-associated outcomes. However, the mechanisms by which bacteria directly neutralize the antimicrobial systems of their rivals remain largely unexplored. Dan Xiong, Jinxing Liao, and their colleagues in Qian's group set out to investigate whether a type IV secretion system (T4SS) can be used to disarm a competitor's antibacterial type VI secretion system (T6SS).
The team found that the ubiquitous soil bacterium Lysobacter enzymogenes employs its bacterial‑killing T4SS to deliver a non‑lethal effector, LqqE1, into the cytoplasm of Pseudomonas putida—a competitor equipped with a functional antibacterial K1‑T6SS. LqqE1 directly binds to VgrG1, a conserved structural component of the K1‑T6SS spike, thereby blocking the native loading of the nuclease effector Tke2 onto VgrG1. Consequently, the translocated LqqE1 abolishes the secretion of the inner‑tube protein Hcp via the K1‑T6SS, effectively disrupting the antibacterial function of P. putida without killing it—a "win without battle" strategy. Structural and phylogenetic analyses further revealed that LqqE1 homologs are widespread among bacteria encoding T4SS, and several representative members exhibit similar T6SS‑disabling activities.
See the article: A T4SS Effector Directly Disarms Competing Antibacterial T6SSs by Hijacking Their Conserved Spike Component
https://doi.org/10.1007/s11427-026-3315-0
Journal
Science China Life Sciences