This application describes feasibility study to extend and apply new DNA fingerprinting methods to 2 periodontal bacteria. The methods involve: in situ extraction of intact genomic DNA from bacteria suspended in agarose blocks; digestion of the DNA by restriction endonucleases to a small number of large fragments; and fractionation of these fragments in agarose by pulsed-field gel electrophoresis. Specifically, I will develop competence in the methods by following published procedures using Escherichia coli as the test organism. I will apply and modify the methods to extract genomic DNA from Streptococcus sanguis biotypes I and II, and from Porphyromonas gingivalis (formerly Bacteroides gingivalis). I will attempt to show differences in DNA fingerprints between the 2 biotypes of Strep. sanguis, and between 3 clinical isolates of P. gingivalis. This will illustrate the levels of differentiation attainable with this method of molecular typing. If this feasibility study is successful my intention is to use the technology in molecular epidemiological studies of periodontal pathogens.