156 A. N. BELOZERSKY AND A. S. SPIRIN 



in. Constituents of Nucleic Acids 

 1. Deoxyribonucleic Acid 



a. Sugar 



At present, there are no grounds to doubt the universal occurrence of 

 2-deoxy-D-ribose as the sole sugar DNA constituent in all representatives 

 of the living world, including the microorganisms. This problem has been 

 reviewed earlier. 79 ' 80 It should be mentioned, only, that special investiga- 

 tions on the identification of 2-deoxyribose were carried out on the DNA 

 of yeast, 81 Mycobacterium tuberculosis avium 81 and Mycobacterium tubercu- 

 losis bovis. 82 



b. Nitrogenous Constituents 



Multiple investigations of the composition of very different DNA showed 

 that the overwhelming mass of nitrogenous constituents consists of com- 

 mon purine (guanine and adenine) and pyrimidine (cytosine and thymine) 

 bases. 80 Microorganisms are no exception in this respect. Moreover, in none 

 of the microorganisms studied, including bacteria, 80 " 86 actinomycetes (our 

 laboratory), yeasts 80 ' 81 - 84 and other fungi (Uryson, our laboratory), algae, 87 

 and protozoa, 88 could 5-methylcytosine be found as a DNA component. 

 The presence of methylcytosine is a characteristic feature of DNA of higher 

 organisms, both animals and plants. 8083 " 86 In the DNA of all the higher 

 plants examined, methylcytosine occurred in a higher proportion than in 

 that of animals. 89 By this characteristic, the DNA of microorganisms shows 

 quite a distinct qualitative difference from that of higher forms. At the 

 same time, the absence of 5-methylcytosine proved a common feature in 

 the DNA of very different groups of microorganisms. 



In 1955, however, Dunn and Smith found a new base, 6-methylamino- 



79 W. G. Overend and M. Stacey, in "The Nucleic Acids" (E. Chargaff and J. N. 



Davidson, eds.), Vol. 1, p. 9. Academic Press, New York, 1955. 

 8 " E. Chargaff, in "The Nucleic Acids" (E. Chargaff and J. N. Davidson, eds.), Vol. 



1, p. 307. Academic Press, New York, 1955. 



81 E. Vischer, S. Zamenhof, and E. Chargaff, J. Biol. Chem. 177, 429 (1949). 



82 T. Tsumita and E. Chargaff, Biochim. et Biophys. Acta 29, 568 (1958). 



83 G. R. Wyatt, Nature 166, 237 (1950). 



Si G. R. Wyatt, Biuchem. J. 48, 581 (1951). 



85 J. D. Smith and G. R. Wyatt, Biochem. J. 49, 144 (1951). 



86 S. G. Laland, W. G. Overend, and M. Webb, /. Chem. Soc. p. 3224 (1952). 



87 E. M. Low, Nature 182, 1096 (1958). 



88 O. Scherbaum, Exptl. Cell. Research 13, 24 (1957). 



89 S. O. Uryson and A. N. Belozersky, Doklady Akad. Nauk S.S.S.R. 125, 1144 

 (1959). 



