Figure 3. Pyoverdine-containing supernatants from producers can both stimulate and inhibit the growth of non-producers.

(A) The likelihood for non-producers to be stimulated by pyoverdine-containing supernatants from a producer did not significantly differ between pond and soil isolates. (B) In contrast, the likelihood for non-producers to be inhibited by producer supernatants was significantly higher for pond than for soil isolates. The supernatant assay involved 53 (soil 26 / pond 27) non-producers, and 142 (70/72) producer supernatants from a subset of communities (12/12), resulting in a total of 303 (152/151) non-producer-supernatant combinations, each replicated three to four times. ‘Stimulation’ or ‘inhibition’ corresponded to cases where non-producers grew significantly better or worse with supernatant than without, respectively. Box plots show the median (bold line), the 1^st and 3^rd quartile (box), and the 5^th and 95^th percentile (whiskers).