Proceedings of the Seventh Mid-Atlantic Regional Extrachromosomal Genetic Elements Conference. September 30-October 2, 1983, Virginia Beach, Virginia. Abstracts.

Several attempts to introduce pJH 1, an 80.7-kb R plasmid from Streptococcus faecalis strain JHI and coding for resistance to kanamycin, streptomycin, erythromycin, and tetracycline (Tc), into S. sanguis by transformation have failed. By using pDL3 10, a hybrid plasmid composed of a loto 12-kb DNA segment of pJH1 that includes the Tc resistance determinant, and intact pJH2, a second plasmid harbored by strain JHl, we recovered six transformants of S. sanguis strain Wicky that were resistant to 7 &ml of Tc on BHI agar plates. Four of these clones contained a plasmid, pDL316, with an apparent size of 4.4 kb, based on EcoRl fragments of 1.55 and 2.8 kb. The two other transformants contained a second plasmid, pDL3 17, that also had two EcoRI sites, yielding fragments of 6.0 and 3.5 kb. One of the original clones containing pDL3 16 was shown subsequently to harbor pDL3 17 only. Purified pDL3 16 transformed competent Wicky cells at a frequency of 8.6 X 10e8 per microgram of DNA, while the transformation frequency with pDL3 17 was 3.7 X IO-‘. Secondary transformants contained the same plasmid as that used in the transformation. Experiments that included EcoRIdigested DNA, agarose gel electrophoresis, Southern blots, and DNA-DNA hybridization with a “P-labeled pDL3 17 probe showed that this plasmid shared no detectable DNA sequence homology with pJH2 or S. sanguis