Abstract
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 deoxy-nucleotides (supplement-1) thanunsupplemented 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 H3-DNA extracted from virulent (S) cells exposed to nonradioactive supplement-1.