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Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III. January 1944.

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Title:	Studies on the Chemical Nature of the Substance [3 of 23]
Alternative Title:	Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III
Creator:	Avery, Oswald T.
Contributor:	MacLeod, Colin M.
Publisher:	Journal of Experimental Medicine
Date:	1944-01-00
Subject:	Cellular signal transduction
Description:	From the Journal of Experimental Medicine Vol. 79, No. 1.
Type:	Text
Format:	text/plain
Language:	en
Identifier:	avery-pg03.jpg
Source:	Master scanned with Epson GT-10000+ flatbed scanner at 600 dpi.
Rights:	http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/copyright.html
Full Text:	OSWALD T. AVERY, COLIN M. MAcLEOD, AND XIACLYN MCCARTY‘39 1. Nutrient Broth.-Beef heart infusion broth containing 1 per cent neopeptone with no added dextrose and adjusted to an initial pH of 7.6-7.8 is used as the basic medium.¢ndividual lots of broth show marked and unpredictable variations in the property of supporting transformation.¢t has been found, however, that charcoal adsorption, according to the method described by MacLeod and Afirick (10) for removal of sulfonamide inhibitors, eliminates to a large extent these variations; conse- quently this procedure is used as routine in the preparation of consistently effective broth for titrating the transforming activity of extracts. 2. Serion or Serous Fluid.-In the first successful experiments on the induction of transformation in vitro, Dawson and Sia (5) found that it was essential to add serum to the medium. Anti-R pneumococcal rabbit serum was used because of the observa- tion that reversion of an R pneumococcus to the homologous S form can be induced by growth in a medium containing anti-R serum.šlloway (6) later found that as- citic or chest fluid and normal swine serum, all of which contain R antibodies, are capable of replacing antipneumococcal rabbit serum in the reaction system.¬ome form of serum is essential, and to our knowledge transformation in vitro has never been effected in the absence of serum or serous fluid. In the present study human pleural or ascitic fluid has been used almost exclusively. It became apparent, however, that the effectiveness of different lots of serum varied and that the differences observed were not necessarily dependent upon the content of R antibodies, since many sera of high titer were found to be incapable of support- ing transformation. This fact suggested that factors other than R antibodies are involved. It has been found that sera from various animal species, irrespective of their immune properties, contain an enzyme capable of destroying the transforming prin- ciple in potent extracts. The nature of this enzyme and the specific substrate on which it acts will be referred to later in this paper. This enzyme is inactivated by heating the serum at 60°-65°C., and sera heated at temperatures known to destroy the enzyme are often rendered effective in the transforming system. Further an- alysis has shown that certain sera in which R antibodies are present and in which the enzyme has been inactivated may nevertheless fail to support transformation.­his fact suggests that still another factor in the serum is essential.­he content of this factor varies in different sera, and at present its identity is unknown. There are at present no criteria which can be used as a guide in the selection of suitable sera or serous fluids except that of actually testing their capacity to support transformation. Fortunately, the requisite properties are stable and remain unim- paired over long periods of time; and sera that have been stored in the refrigerator for many months have been found on retesting to have lost little or none of their original effectiveness in supporting transformation. The recognition of these various factors in serum and their r61e in the reaction system has greatly facilitated the standardization of the cultural conditions required for obtaining consistent and reproducible results. 3. The R Strain (R36A).-The unencapsulated R strain used in the present study was derived from a virulent "S" culture of Pneumococcus Type II. It will be recalled that irrespective of type derivation all "R" variants of Pneumococcus are characterized by the lack of capsule formation and the