[Physicochemical and biological properties of the DNA of virulent and temperate Erwinia carotovora phages].

DNA of virulent and moderate E. carotovora viruses, of marked AT-type, was shown to have molecular weights determine by 2 independent methods from 49.2 to 54 and 28 to 29.8 MD, respectively. The genomes of the viruses under study differed by the point and curve profiles of the melting temperature and sedimentation constant. DNA of the moderate phage contains an unidentified abnormal base and has no free cohesive ends. DNA of the moderate virus contains 15% of nucleotide sequences homologous with those of the virulent virus DNA. Calcium-competent cells are the most acceptable system for the study of DNA transfection of these phages. The virulent virus DNA gives a higher yield of transfectants (by 2 orders) than that of the moderate virus. Herring DNA reduces the level of DNA transfection of both phages approximately by 100-fold. In competitive transfection experiments, the virulent virus DNA was found to be more competitive.