Characterization of a Streptococcus mutans serotype e plasmid pJEB110.

A search for extrachromosomal elements in 300 mutans streptococcal strains, isolated from dental plaque, yielded one 5.7 kb plasmid (pJEB110) in a serotype e strain (JEB110). The strain was distinguished from a plasmid-free (B2) and a plasmid-carrying (LM7) serotype e strain, by the presence of a prominent protein band of Mr 70 K on electrophoretograms of buffer-extracted denatured cell protein. Restriction enzyme site mapping indicated that pJEB110 was more closely related to pAM7, the plasmid endogenous to LM7, than to the other Strep. mutans plasmids harboured by serotype c or f strains.