Schematic representation of the knockout strategy to construct the epsC insertional mutation in W83. A. The genetic arrangement of the 3'-end of the CPS locus in the W83 wild type strain with the grey rectangles representing the genes present. B. Construct pΔepsC for insertional inactivation of epsC. The 1.2 Kb epsC was inserted into BamH I-EcoR I digested pGEX-6-p3 (oval) and interrupted by insertion of a 1.2 Kb EryF (shaded rectangle) in the single ClaI restriction site present. The dashed lines between A and B show the homologous crossover regions between the plasmid and W83 CPS locus. C. The final arrangement of the 3'-end of the P. gingivalis CPS locus after double crossover showing the insertional inactivation of epsC. Arrows represent the primers used to confirm the integrity of the epsC mutant.