Bacterial strains and culture conditions
Pseudomonas fluorescens SS101 (Pf SS101) was cultured in King’s medium B (KB), while Microbacterium EC8 (MB) was cultured in Tryptone Soy broth (TSB) medium and Paraburkholderia graminisPHS1 (Pbg ) in Luria Bertani (LB) medium (Lennox, Carl Roth) at 25 °C for 16h. Bacterial cells were collected by centrifugation, washed three times with 10 mM MgSO4, and resuspended in 10 mM MgSO4 to a final density of ~109 cells/ml (OD600 = 1.0).