Biocontrol of Soft Rot: Confocal Microscopy Highlights Virulent Pectobacterial Communication and Its Jamming by Rhodococcal Quorum-Quenching
Résumé
Confocal laser-scanning microscopy was chosen to observe the colonization and damage caused by the soft rot Pectobacterium atrosepticum and the protection mediated by the biocontrol agent Rhodococcus erythropolis. We developed dual-color re- porter strains suited for monitoring quorum-sensing and quorum-quenching activities leading to maceration or bio- control, respectively. A constitutively expressed cyan or red fluorescent protein served as a cell tag for plant colonization, while an inducible expression reporter system based on the green fluorescent protein gene enabled the simultaneous re- cording of signaling molecule production, detection, or deg- radation. The dual-colored pathogen and biocontrol strains were used to coinoculate potato tubers. At cellular quorum, images revealed a strong pectobacterial quorum-sensing ac- tivity, especially at the plant cell walls, as well as a concomitant rhodococcal quorum-quenching response, at both the single- cell and microcolony levels. The generated biosensors appear to be promising and complementary tools useful for molecular and cellular studies of bacterial communication and interference.