Biofilm assay of MR-1 and aggA mutant. (A) Pellicle formation of MR-1, ΔaggA, ΔaggA* (aggA in-frame deletion mutant containing pBBR-AGGA). (B) SSA Biofilm was assessed for the strains indicated after 16 and 24 h, respectively. Cultures were prepared as described in Methods. The averaged OD readings of four independent culture tubes were given with images of representative CV-stained tubes.