Bacterial communication mediated by T4SS effectors

Abstract Bacteria have the ability to inhibit the growth of competitors by using contact-dependent killing devices, such as the bacterial-killing type IV secretion system (T4SS). A recent publication in The ISME Journal by Wang et al. (ISME J, 2023. https://doi.org/10.1038/s41396-023-01533-7 ) uncovered that T4SS could deliver a unique “non-toxic” effector protein, LtaE, into interspecies bacterial cells. The delivery of LtaE by the bacteria Lysobacter enzymogenes induces the antifungal antibiotic 2,4-DAPG production by binding to the transcriptional repressor PhlF in another bacterial species, Pseudomonas protegens. As a result, P. protegens regains the capacity to protect plants from nearby fungal infections. This finding uncovered a novel role of T4SS in mediating interactions of interkingdom cooperation to kill microbial competitors in soil microbiomes.