Scanning laser confocal microscopy images of anode biofilms of G. sulfurreducens strains heterologously expressing pilin genes from (a) F. sinusarabici, (b) C. nitroreducens, (d) D. alkaliphilus and (d) Ca. D. auxilii. Top-down three-dimensional, lateral side views (right image) and horizontal side views (bottom image) show cells stained with LIVE/DEAD BacLight viability stain. Bar, 50 μm. Mean and s.d. for biofilm thickness at 100 points in each biofilm: F. sinusarabici, 26.1±5.2 μm; C. nitroreducens, 41.0±6.6 μm; D. alkaliphilus, 41.7±6.6 μm; Ca. D. auxilii, 10.7±2.1 μm.