A Robust Method to Perform In Vitro and In Planta Interbacterial Competition Assays: Killing Plant Pathogens by a Potent Biocontrol Agent

Interbacterial competition assays have become an essential tool for understanding the interactions between bacteria and their ability to outcompete one another in natural environments. This is especially relevant when studying the type VI secretion system (T6SS), a contact-dependent bacterial weapon that can be used to kill or inhibit the growth of other competing bacteria. Some beneficial environmental microorganisms such as Pseudomonas putida rely on the T6SS as their primary biocontrol mechanism to eliminate resilient plant pathogens. Competition assays are an essential methodology in this field that allows us to understand the efficacy of this bacterial nanoweapon. This chapter outlines the methodology for conducting in vitro and in planta competition assays between P. putida, a well-known biocontrol agent, and phytopathogenic bacterial species of economic and scientific interest.