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This paper describes the results obtained in experiments on interspecific transformation in Azotobacter. When Axotobacter chroococcum was transformed with the DNA of A. vinelundii 6-10 7' of the colonies differed from the parent strain in colour, colony character and biochemical characteristics. Some of the transformant strains had higher nitrogen-fixing capacities than had the receptor strain. Transformants obtained by treatment of A. vinelandii with the DNA of A. chroococcum also had different colour, colony characteristics and capacity to grow in nutrient broth and peptone, but their nitrogen-fixing capacity was decreased. 0.1 M-EDTA, pH 8.0); 1.5 g. sodium citrate and 2.5 ml. of a 1 % (wlv) solution of Vol. 40, No. 3 was issued '

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The transformability of 25 strains of yeasts belonging to 23 species in three genera -Sacciiaromjw.~, Hansenula and Candida -was investigated with respect to ten characters. Eighteen hour cultures at about the end of the log phase of growth, addition of 10 p g DNA/ml, and an incubation time of 30 min at 30 to 37 "C usually yielded best results. Of the 109 pairs of strains investigated I I yielded positive results, which included intraspecific, interspecific and intergeneric transformation. Three adenine-requiring mutants of S. cerevisiue were transformed to prototrophy with the DNA of S. cereiisiae var. dlipsoideus. DNA of the latter strain also transformed three other species of Saccharomyces. In Candida, reciprocal transformation was observed between C. utilis and C. lipolytica. Hansenula petcv-sonii transformed H. .jadinii to rhamnose utilization. I n intergeneric experiments, H . mrukii was transformed with s. cerevisiae var. ellipsoideci.v DNA and C. uti1i.r with the DNA from H . petersonii. Attempts at transformation between Saccharomyces and Candida were unsuccessful. The GC content of DNA from the strains which yielded positive results varied from 36.0 to 37.3 mol %. The implications of these findings for the inter-relationships and taxonomy of yeasts are discussed.