Distribution of Deoxyribonuclease in Anti-R Pneumococcal Sera and its Relation to Transformation Reaction

Abstract

IN previous communications dealing with the mechanism and the external factors required in transformation of type in Pneumococcus it was shown¹ that in some cases a positive transformation result can only be achieved by properly activating and then inactivating the donor DNA together with small doses of pancreatic DNase in the presence both of an inhibitor (sodium citrate) and an activator of the DNase (Mg²⁺). As it was shown later², this intricate system had to be used in such cases where anti-R pneumococcal sera with a high residual intrinsic activity of DNase after heat inactivation have been used in the transformation medium. Although the importance of the citrate as an inhibitor of the DNase appeared to be explained, the question of minute amounts of DNase being absolutely indispensable in this system remained quite obscure. It seemed as if a complete blockade of the DNase caused by citrate was not desirable for the transformation reaction. The present study is concerned with the problem of the distribution of DNase in various fractions of the anti-R pneumococcal sera used in our transformation experiments and aims to approach nearer to the question of the possibly active role of DNase in the transformation reaction.