Deoxyribonucleate (DNA) preparations from elicited genetic transformation of recipient cells, and . The frequency was low (0·0005% transformation for the most reactive of six strains), as might be expected of an interaction between two organisms as dissimilar as a rod and a coccus. Evidence that the hereditary change (attainment by susceptible cells of resistance to 500 μg. dihydrostreptomycin/ml.) was due to transformation was provided by the typical time course of the reaction, the typical linear response to decreasing concentrations of DNA below 0·1 μg./ml., and by tests of transforming activity of DNA preparations extracted from 11 dihydrostreptomycin-resistant () strains which arose by intergeneric transformation. These DNAs had relatively high transforming activity for recipient strains of both species. Thus, the region of the transforming DNA molecule from a transformant strain of was recognized and genetically integrated by populations of recipient cells at frequencies as much as 10,000 times higher than those of DNA from strains of (derived by spontaneous mutation). The results with DNA preparations from particular transformants are interpreted as indicating that the length of a DNA nucleotide sequence which is integrated by a cell during transformation may differ for different cells of the same treated population.


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