Characterization and physical mapping of plasmids of black-pigmented Bacteroides.

Eight species of black-pigmented Bacteroides (BPB) were examined for plasmid content. Three classes of plasmids with molecular sizes of 16.0 kilobase (kb), 5.4 kb and 5.0 kb were found in 7 of 125 Bacteroides intermedius strains. One strain each of Porphyromonas (former Bacteroides) asaccharolyticus and of Bacteroides levii were also shown to have plasmids. However, no plasmids were detected in 90 strains of Porphyromonas (Bacteroides) gingivalis. The plasmids were purified and digested with restriction endonucleases for restriction mapping. The maps obtained in this study have given us information on the scheme of constructing recombinants which may be usable as shuttle vectors, by the recombination of BPB and Escherichia coli plasmids.