Test for adhesion to sand (A-C) and biofilm formation on PVC (D-F) tabs of the studied strains marked with GFP. The wild-type strain formed three-dimensional structures (A, D) whereas ANU843ΔC2 established microcolonies forming a layer that coated the surface (B, E), and ANU843C2+ barely adhered (C, F). Bar (A-F) 500 μm. (G) We also evaluated attachment quantitatively, by counting cfus of bacteria attached to sand grains. Error bars indicate the standard deviation. Each experiment was repeated three times. Values followed by the same letter do not differ significantly according to the Fisher protected LSD test at P = 0.01.