Transformation of Streptococcus sanguis Challis by plasmid deoxyribonucleic acid from Streptococcus faecalis

Abstract

Plasmid DNA from S. faecalis, strain DS5, was transferred to the Challis strain of S. sanguis by transformation. Two antibiotic resistance markers carried by the .beta. plasmid from strain DS5, erythromycin and lincomycin, were transferred to S. sanguis at a maximum frequency of 1.8 .times. 10-5/colony-forming unit. Approximately 70% of the covalently closed circular DNA isolated from transformant cultures by dye buoyant density gradients was shown to be hybridizable to .beta. plasmid DNA. Two major differences were observed between the .beta. plasmid from S. faecalis and the plasmid from strain DS5 sedimented in velocity gradients at 43S, but the covalently closed circular DNA from transformed Challis sedimented at 41S, suggesting a 1.5-Mdal deletion from the .beta. plasmid occurred; although the 43S .beta. plasmid remained in the supercoiled configuration for several weeks after isolation, the 41S plasmid was rapidly converted to a linear double-stranded molecule. Attempts to transform S. sanguis with the .alpha. plasmid from S. faecalis, strain DS5, were unsuccessful.