SUMMARY: We attempted to transform proflavine-sensitive strains of to proflavine resistance by growth in the presence of deoxyribonucleic acid-containing extracts from resistant organisms. Three methods were used to obtain the DNA preparations. Method 1 (Boivin, 1947) did not give active transforming principle, even when a variety of modifications was introduced. Method 2 (McCarty & Avery, 1946) and Method 3 (Mayers & Spizizen, 1954) gave extracts which were active in transformation. With DNA prepared by Method 2, an increase in the number of resistant organisms was found in one of four rough sensitive strains. We concluded that only a small proportion of the organisms of this strain were competent. We were able to increase the proportion of these competent organisms by a method of ‘double replica plating’. According to Method 3, organisms were lysed by sodium dodecylsulphate (Duponol) in presence of citrate, and protein removed by sodium acetate. From the supernatant fluid transforming principle was precipitated by acidified ethanol, and then dissolved in saline. The smooth strain of used in most of our experiments served as the recipient strain. The transforming principle from resistant organisms was not active alone, but was active in the presence of the protein precipitate. The activity appeared to be lost when the transforming principle was treated with DNAase. No activity was shown by extracts from sensitive organisms. The activation of transforming principle by the protein precipitate is thought to be due to the Duponol carried with it. Duponol appears to inhibit DNAase, so that it might act by preserving transforming DNA from destruction by the enzyme present in the recipient organisms. Our experiments did not always give positive results. Whilst we believe that we have demonstrated transformation in this system, the low reproducibility of our results makes it necessary to repeat and extend.


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