The insectidical toxin is expressed by P. protegens CHA0 only in certain insect species and not on plant roots. (A) Epifluorescence microscopy of hemolymph isolated from S. littoralis, T. molitor and A. pisum infected with FitD-mCherry reporter strains with the wild-type (CHA1176) and ΔfitH mutant (CHA1178, positive control) background. The bacteria harbor a constitutive GFP cell tag for identification, expression of FitD-mCherry can be seen in the DsRed channel. Strain CHA0-gfp2 was used as a negative control. Bars represent 10 µm, micrographs are false-colored. The experiments were performed at least twice with similar results. (B) Epifluorescence microscopy of plant roots (or root washes) three to five days after the inoculation with the same reporter strains as in panel A, with or without co-inoculation with the phytopathogen Fusarium oxysporum f. sp. radicis-lycopersici. The experiments were performed twice with similar results.