Figure 6

Biofilm analysis of the mp65Δ mutant. (A) CV staining. Equal numbers of cells from the wild type (wt), mp65Δ mutant (hom) and revertant (rev) strains were suspended in 250 μl of RPMI medium and incubated in 24-well plates for 48 h at 37°C. Non-adherent cells were then removed by washing, and adherent cells were stained with CV. The biofilms were visualized before (Panel 1) and after (Panel 2) staining and then captured by using either a Gel Doc system (Bio-Rad), or using an inverted microscope at 40x magnification (Panel 3). (B) XTT assay. The colorimetric XTT assay, which determines the metabolic activity of the cells, was used to quantify the biofilms of the wild type (wt: grey column), mp65Δ mutant (hom: white column) and revertant (rev: black column) strains. Each result is the mean of 3 independent experiments (P≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom vs. wt and rev strains; error bars represent standard deviations). (C) Dry weight determination. The dry weight determination, which measures the total biomass of the cells, was used to quantify the biofilms of the wild type (wt: black column), mp65Δ mutant (hom: grey column) and revertant (rev: white column) strains. Results were normalized to wt, which was taken as 100%. Each result is the mean of 3 independent experiments (P ≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom versus wt and rev strains; error bars represent standard deviations.