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bioRxiv · 10.1101/2025.01.11.632536

Tke5 is a novel Pseudomonas putida toxin that depolarises membranes killing plant pathogens

Velazquez, C.·Arce-Rodriguez, A.·Altuna-Alvarez, J.·Rojas-Palomino, J.·Flores-Ceron, A.·Ruiz, A.·Gonzalez-Magana, A.·Queralt-Martin, M.·Alcaraz, A.·Albesa-Jove, D.·Bernal, P.
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Abstract

The soil bacterium Pseudomonas putida injects toxic proteins into neighbouring competitors, including resilient phytopathogens, using the Type VI secretion system (T6SS). The secretion of toxins endows P. putida with a significant fitness advantage, allowing this biocontrol agent to thrive in plant-related polymicrobial environments and prevent phytopathogen infections. Despite its agricultural significance, the toxin repertoire of P. putida, particularly those secreted via the K2- and K3-T6SSs, remains poorly understood. We present the first comprehensive molecular study of Tke5, a potent toxin encoded within the K3-T6SS, which represents the first comprehensive functional analysis of the BTH_I2691 protein family. Our biophysical data demonstrate that Tke5 is a pore-forming toxin that disrupts bacterial membranes through selective ion transport, inducing membrane depolarisation and cell death. Unlike conventional detergent-like pore-forming toxins, Tke5 preserves overall membrane integrity, avoiding large, non-specific disruptions. This unique mechanism offers a powerful approach to targeting resilient phytopathogens. This study reveals a previously undescribed mode of action within a widespread yet understudied toxin family. Our findings highlight the potential of P. putida as a biocontrol agent, offering alternatives to chemical pesticides by exploiting novel toxin mechanisms. Understanding these bacterial toxins is crucial for developing effective strategies to combat plant pathogens.

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Velazquez, C., Arce-Rodriguez, A., Altuna-Alvarez, J., Rojas-Palomino, J., Flores-Ceron, A., Ruiz, A., Gonzalez-Magana, A., Queralt-Martin, M., Alcaraz, A., Albesa-Jove, D., Bernal, P.. 2025-01-12. Tke5 is a novel Pseudomonas putida toxin that depolarises membranes killing plant pathogens. https://doi.org/10.1101/2025.01.11.632536

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