BB precursors are “public goods”; (A) BB is produced by the biosynthetic enzymes DhbACEBF from chorismate to 2,3-DHB, which is then used as a starting unit by the nonribosomal synthase complex DhbEBF to cyclize three monomers of 2,3-DHB using glycine (Gly) and threonine (Thr) linkers; (B) relative colony areas of PS92 and individual ΔdhbA-F gene deletion mutants; (C) relative colony areas of PS92 and combinations of ΔdhbA-F gene deletion mutants; black dashed lines and grey rectangles denote the mean relative colony size in the DK1042 + PS92 interaction (lines = mean, rectangles = min and max); red dashed lines and rectangles denote similarly for the ΔdhbA + PS92 interaction; grouping letters are from ANOVA with Tukey–Kramer’s post hoc test; identical letters within each plot indicate a statistically significant grouping (P < .05, n > 8, from three independent experiments).