FIG. 1.

Positive and negative signaling by wheat rhizobacteria. Random strains from a collection of rhizosphere bacteria isolated from wheat roots were spotted onto a white lawn of strain 30-84I (PhzI⁻) (left) or an orange lawn of wild-type strain 30-84 (right). (Left) Positive cross-communication is indicated by the orange halos surrounding the spots, indicating rescue of phenazine production. (Right) Negative cross-communication is indicated by the white halos surrounding the spots, indicating inhibition of phenazine production.