When cultured in TSB as free-living cells, wild type and all mutant strains showed the similar growth rates, as reported in previous FK228 study [20]. In contrast, when incubated in PBS for 24 h, wild type and mutants lacking long and/or short fimbriae formed distinct biofilms (Figure

1 and Table 1). Wild type strain 33277 formed biofilms with a dense basal monolayer and dispersed microcolonies. Compared with the wild type, the long fimbria mutant KDP150 formed patchy and sparser biofilms with a significantly greater distance between fewer peaks, although mean peak height was almost the same as that of the wild type strain. In contrast, the short fimbria mutant MPG67 developed cluster and channel-like selleck products biofilms consisting of significantly taller microcolonies compared to the wild type. Similar to MPG67, the mutant (MPG4167) lacking both types of fimbriae also formed thick biofilms with significantly taller microcolonies than the wild type. Viability of the cells in biofilms of each strain was tested by colony count and confirmed at 24 h (data not shown). These results suggest that the long fimbriae are involved in initial attachment and organization of biofilms by P. gingivalis, whereas the short fimbriae have a suppressive regulatory role for these steps. Figure

1 Homotypic biofilm formation by P. gingivalis wild-type strain and mutants in PBS. P. gingivalis strains were stained with CFSE (green) and incubated in PBS for 24 hours. After washing, the biofilms that developed on the coverglass ID-8 were observed with a CLSM equipped with a 40× objective. Optical sections were obtained along the z axis at 0.7-μm intervals, and images of the x-y and x-z planes were reconstructed

with an imaging software as described in the text. Upper panels indicate z stacks of the x-y sections. Lower panels are x-z sections. P. gingivalis strains used in this assay are listed in Table 4. The experiment was repeated independently three times with each strain in selleck compound triplicate. Representative images are shown. Table 1 Features of biofilms formed by P. gingivalis wild-type strain and mutants in PBS   Peak parametersa) Strain Number of peaks Mean distance between peaks (μm) Mean peak height (μm) ATCC33277 (wild type) 28.5 ± 3.3 3.0 ± 0.2 2.8 ± 0.4 KDP150 (ΔfimA) 14.7 ± 2.4** 5.4 ± 1.0** 2.7 ± 0.8 MPG67 (Δmfa1) 29.3 ± 2.0 3.6 ± 0.2 16.6 ± 0.8** MPG4167 (ΔfimAΔmfa1) 30.5 ± 1.9 3.1 ± 0.2 12.7 ± 0.5** KDP129 (Δkgp) 25.5 ± 2.1 3.6 ± 0.3 12.7 ± 1.3** KDP133 (ΔrgpAΔrgpB) 13.0 ± 2.6** 8.4 ± 1.3** 23.2 ± 2.8** KDP136 (ΔrgpAΔrgpBΔkgp) 30.5 ± 2.4 3.2 ± 0.2 12.7 ± 0.7** a) Number of peaks was evaluated in an area sized 90 (x axis) × 2 (y axis) μm. The mean ± SE of 10 areas was shown. **p < 0.