A research team led by David Albesa-Jové, an Ikerbasque Research Professor at the Biofisika Institute (CSIC, UPV/EHU), together with the laboratory of Patricia Bernal at the University of Seville, has revealed with unprecedented detail the molecular mechanisms that allow the beneficial bacterium Pseudomonas putida to eliminate plant pathogens.
The study, published in the prestigious journal The EMBO Journal, shows how this microorganism acts as a true natural bodyguard for crops, reinforcing its role as a biological control agent.
Pseudomonas putida is no ordinary bacterium: it protects plants by eliminating their natural enemies—phytopathogens—through a sophisticated attack mechanism known as the Type VI Secretion System (T6SS), a genuine nanomachine capable of injecting toxins directly into rival bacterial cells. Using high-resolution cryo-electron microscopy, the researchers were able to precisely describe how one of the key components of this system works: the Tke5 toxin.
The results show that Tke5 is a highly efficient modular toxin. Its alpha-helical region forms the toxic core responsible for creating pores in the membrane of pathogenic bacteria, disrupting their ionic balance and causing cell death without compromising overall cell integrity. In contrast, the beta-sheet–rich region acts as a receptor-binding domain, enabling the toxin to anchor specifically to the rival cell membrane and ensuring the effectiveness of the process.
Article reference: Velázquez, C., Zabala-Zearreta, M., et al. (2026). Structural insights into the antibacterial function of the Pseudomonas putida effector Tke5. The EMBO Journal. https://doi.org/10.1038/s44318-025-00689-6
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