title: Transformation of group F streptococci by plasmid DNA.
abstract: When the Challis strain of Streptococcus sanguis was transformed by the 17 megadalton beta plasmid from Streptococcus faecalis strain DS5, the plasmid underwent a 1.5 megadalton deletion (LeBlanc & Hassell, 1976). Furthermore, the covalently closed circular (CCC) plasmid DNA isolated from Challis transformants was rapidly converted to a linear form which did not possess any detectable transforming activity. To obtain stable CCC plasmid DNA a competent culture of a Lancefield group F streptococcus, strain DL8 (ATCC 12393), was used as a recipient of beta plasmid DNA. The plasmid DNA isolated from group F transformants exhibited the same configuration and size characteristics as the DS5 beta plasmid, and the CCC configuration was stable upon storage. CCC plasmid DNA from a group F transformant was biologically active and, when added to competent cultures of strain DL8, transformed them at frequencies about 100-fold greater than did beta plasmid DNA from DS5. This suggests the existence of a restriction--modification system in strain DL8.
mesh_terms: D004270:DNA, Circular / Q000235:genetics; D004352:Drug Resistance, Microbial; D013293:Enterococcus faecalis / Q000235:genetics; D004917:Erythromycin / Q000494:pharmacology; D010957:Plasmids; D013291:Streptococcus / Q000187:drug effects / Q000235:genetics*; D014169:Transformation, Bacterial
chemical_list: D004270:DNA, Circular; D004917:Erythromycin