Quantification of homotypic biofilms formed by P. gingivalis wild-type strain and mutants in PBS. Biofilms were formed as described in Figure 1, and 10 fields per a sample were randomly recorded and quantified with a CLSM. Z stacks of the x-y sections were converted to composite images to quantify each biovolume as described in the text. Standard error bars are shown. Statistical analysis was performed using a Scheffe test. *p < 0.05 and **p < 0.01 in comparison to the wild-type strain. P. gingivalis strains used in this assay are listed in Table 4.