Firshein, W. (Wesleyan University, Middletown, Conn.). Effects of deoxyribonucleic acid products on deoxyribonucleic acid synthesis of virulent and avirulent pneumococci. J. Bacteriol. 82:169-180. 1961.-Cell suspensions of virulent pneumococci synthesize a greater amount of deoxyribonucleic acid (DNA) per cell in the presence of DNA + deoxyribonuclease + mixtures of deoxynucleosides and deoxynucleotides (supplement-1) than unsupplemented suspensions. Under identical conditions, avirulent and weakly virulent pneumococci do not respond to these DNA breakdown products. Glucose and casitone must be present for maximal effects to occur.A DNA turnover occurs in virulent cells. This has been demonstrated by a decrease in specific activity of H(3)-DNA extracted from virulent (S) cells exposed to nonradioactive supplement-1.