Transformation Reaction of Pneumococci in the Absence of Serum Factor

Abstract

CONTRARY to the general proposition that transformation reactions of pneumococci cannot take place in the absence of serum factor^1–3, our experiments^4,5 indicated that cells of R36NC, a pneumococcal rough strain derived from 11-D39S, could be transformed to streptomycin-resistant ones by means of purified deoxyribonucleate in diffusate media. But in these experiments, deoxyribonucleate was kept present throughout the culture growth and the cultivation was continued overnight before plating on streptomycin plates, so that the population change after the occurrence of transformation reaction might have distorted the results. This possibility was completely excluded in the present experiment by the use of deoxyribonuclease, which was added to the reaction mixture to stop the action of deoxyribonucleate at a definite time.