FIG 2.

Live/dead bacterial viability assay by confocal microscopy. Stained in green are the viable cells, and stained in red are the dead cells. We used two control strains: E. coli and S. mitis. (A) Control S. mitis biofilm to which S. mitis cells were added. (B) Control S. mitis biofilm to which E. coli cells were added. (C) S. mitis biofilm to which P. gingivalis was added. (D) Box plot showing the results for biomass calculated using a COMSTAT v1.1 program (19). The y axis represents the ratio of dead to live cells after the addition of the different organisms indicated in the x axis. Significance was tested by a Kruskal-Willis rank sum test with an asterisk (*) representing groups with significant differences at P < 0.05. Analysis was performed for three independent biological experiments (n = 3) with a series of 20 sections. The dark line in the box represents the median. The two section in the box represent the upper and lower quartiles. Bars (whiskers) represent the maximum and minimum values in the data sets.