FIG. 4.

Clinical samples examined for the presence of multiple strains of P. gingivalis by heteroduplex analysis. DNA amplified from each sample was examined by itself. The first lane contains DNA size markers: phage lambda digested with the restriction enzymes EcoRI and HindIII. The sample in lane 4 formed only the homoduplex band, indicating the presence of a single strain. The samples in lanes 2 and 5 each show a heteroduplex doublet, indicating the presence of two strains of P. gingivalis. The sample in lane 3, with two heteroduplex doublets, contains three strains of P. gingivalis.