title: Characterization of the Streptococcus mutans plasmid pva318 cloned into Escherichia coli.
abstract: We further characterized the cryptic plasmid pVA318 of Streptococcus mutans. It had a contour length of 5.64 +/- 0.26 kilobases and a guanine-plus-cytosine content of 32 to 34 mol %. Upon cloning the pVA318 plasmid into the vector pBR322 in Escherichia coli, we made the following observations. The expression of tetracycline resistance by HindIII-cloned chimeras, where the insert was in the tetracycline resistance promotor, depended on the orientation of the pVA318 insert. Both HindIII-cloned chimeras segregated from polA(Ts) cells at a nonpermissive temperature. Chimeric molecules cloned with PstI initially showed much instability; the reason for this is unknown, although stable variants were obtained. Both HindIII-cloned variants and a PstI-cloned chimera produced a pVA318-specific protein of approximately 20,000 molecular weight in E. coli minicells. The biological function of this protein is not known; it had no bacteriocin activity against S. mutans or group A Streptococcus indicator strains, and it did not appear in the E. coli periplasm. We constructed a map of pVA318 for restriction endonucleases HindIII, HpaI, PstI, and HaeIII. A previously reported BamHI site in pVA318 did not appear in the pVA318 portion of any of our chimeric clones.
mesh_terms: D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D008970:Molecular Weight; D010641:Phenotype; D010957:Plasmids; D011815:R Factors; D013295:Streptococcus mutans / Q000235:genetics*; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D004269:DNA, Bacterial; D004262:DNA Restriction Enzymes; D013752:Tetracycline