Contribution on the biochemical investigation of external factors required for type transformation in the pneumococcus.

Abstract

(1) It was found that different anti-R-Pneumococcus sera display a great variability in DNase activity contained therein. There are sera in which a high DNase activity remains even after inactivation at 65° C for 30 min. At dilutions which are commonly used in the experiments a certain residual activity is always found. (2) The presence of suitable concentrations of salts with univalent cations in the transformation medium inhibits the DNase activity in it, thus regularizing the results obtained during type transformation in the Pneumococcus. This explains the results of our earlier work concerning the significance of these salts in the transformation reaction even if their role is manifold. (3) By preliminary estimation of DNase activity in sera or serous fluids, globulin and albumin preparations, it can readily be shown whether these sera are or are not suitable for supporting the transformation reaction. Antisera with a high residual activity of DNase do not support the transformation reaction unless DNase had been suitably inhibited. (4) High DNase content in serum may by inhibited by higher temperature or occasionally by increased salt concentration. By using a mixture of citrate, magnesium ions and a small amount of pancreatic DNase activated for 15 min. at 30° C and then inactivated for 15 min. at 60° C, together with DNA, a positive result may be achieved during transformation using some antisera with a high DNAse activity which will not allow such a reaction to proceed without the agents added. (5) The transformation reaction always takes place in the presence of a small amount of DNase which is blocked by different factors in the system. The possible active role of DNase in the transformation reaction is discussed. The author is indebted to Academician I. Malek for the interest with which he followed the entire work described. Technical assistance of PhMr. P. Křeckova and Mr. J. Kubicek is acknowledged. Our thanks are due to Dr. Hilgert of the Institute of Experimental Biology and Genetics for a sample of DNA from chick erythrocytes.