FIG 5.

Conditioned medium from Pseudomonas protegens (ES558) reduced root association and liquid survival of 10 additional L. monocytogenes strains. Conditioned medium (CM) was collected by centrifuging and filter sterilizing the liquid from bacteria grown with hydroponic plants after 24 h of incubation at RT and then used fresh. CM from either L. monocytogenes strains (as a control) or ES558 were mixed at a 1:1 concentration (0.5× fresh MS to 0.5× CM) in the assay. L. monocytogenes numbers of CFU/plant (A) and CFU/ml (B) were determined by serial dilution on 1× LB. Statistics were performed using Mann-Whitney t tests comparing number of CFU of L. monocytogenes grown in its own CM to L. monocytogenes grown in ES558 CM. Asterisks denote P values (*, P < 0.05; **, P < 0.01; ***, P < 0.001). Dashed lines indicate the level of detection. If samples were undetected, they were assigned a value immediately below the level of detection.