Fig 7. MrpH-dependent biofilm formation occurs on urinary catheter segments.

Pieces of a silicone Foley catheter were added to culture tubes containing Minimal A, pH 6. Medium was inoculated 1:100 with overnight culture of P. mirabilis, and cultures were aerated at 37C for 24 h. Catheter segments were stained with crystal violet, then removed to a new tube for extraction and quantification of stain. (A) biofilm formation by P. mirabilis HI4320 (wt), L-ON, and L-OFF strains shown in previous figures (n = 3). (B) biofilm formation by an independently constructed locked ON strain (mrpI-ON), a double mutant (mrpI-ON ΔmrpH), and the double mutant complemented with a plasmid containing either luciferase (lux) or mrpH, both under the native mrp operon promoter (Pmrp) (n = 5–6). Statistical significance was assessed versus mrpI-ON. (C) a representative example of biofilm formation by the strains shown in B.