Fig. 2: Involvement of Sfp-dependent secondary metabolites on the inhibitory effect of B. subtilis 3610 on curli production.

a Macrocolony biofilms of E. coli W3110 grown on CR-containing salt-free LB agar alone or in close interaction with macrocolonies of B. subtilis 3610 wt or a derivative strain deficient in the phosphopantetheinyl transferase (sfp). The lower images are enlarged view of the E. coli macrocolonies shown in the upper images that magnified the zone of interaction with B. subtilis 3610. The images show that the lack of Sfp renders B. subtilis unable to inhibit curli. Yellow and light blue scale bars in (a) represent 5 and 0.5 mm, respectively, and are applicable to all images in the panel. b Chemical structures of three Sfp-dependent secondary metabolites produced by B. subtilis 3610: surfactin and plipastatin, both NRPs, and bacillaene, a hybrid PK-NRP compound. c Macrocolonies of E. coli W3110 grown on CR-containing salt-free LB agar in close interaction with macrocolonies of B. subtilis 3610 strains deficient in surfactin (srfAC), plipastatin (ppsC) or bacillaene (pksL). The images show that in the absence of bacillaene only, curli production and hence the curli-dependent biofilm morphology occur normally. Yellow and light blue scale bars in (c) represent 5 and 0.5 mm, respectively, and are applicable to all images in the panel.