Fig. 2: Microscopy images of B. subtilis biofilms.

The mature biofilms were grown on agar-filled 3D-printed chamber slides and observed in situ. a, b Bright-field images taken by air objectives of WT and ∆eps B. subtilis biofilm surface, respectively. Scale bars represent 50 μm. c 3D-reconstructed CLSM image of upper 40 μm of WT biofilm. d 3D-reconstructed CLSM image of the upper 10 μm of ∆eps biofilm. e, f CLSM slice through the biofilm structure of WT and ∆eps biofilm, respectively. All CLSM images were taken by silicon oil objective. Scale bars represent 10 μm. To exclude pleiotropic effects as the main cause of the observed biofilm structural differences, further experiments were performed (Fig. 3).