Characterization of the Streptococcus mutans plasmid pVA318 cloned into Escherichia coli

J. B. Hansen, Y. Abiko, R. Curtiss

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


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 promoter, 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.

Original languageEnglish (US)
Pages (from-to)1034-1043
Number of pages10
JournalInfection and immunity
Issue number3
StatePublished - 1981
Externally publishedYes

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases


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