184 A. N. BELOZERSKY AND A. S. SPIRIN 



TABLE XIII 



RNA Composition of Original Intestinal Bacteria and Their 



Experimentally Produced Forms* 



Form of bacteria 



Base proportions 



(moles %) (G + U)/ (G + C)/ 



(A + C) (A + U) 



c; 



Escherichia coli 



Original 



Neutral form 



Alkali-producing form 

 Salmonella typhosa 



Original 



Neutral form 



Alkali-producing form 

 Shigella dysenteriae 



Original 30.4 25.9 24.4 19.3 0.99 1.21 



Alkali-producing form 30.5 25.8 23.8 19.9 1.02 1.19 



Alkali-producing form 29.9 26.9 23.8 19.4 0.97 1.16 



* Taken from A. S. Spirin, A. N. Belozersky et al., Biokhimiya 23, 154 (1958). 



like microbe isolated from the human urethra. 172 The DNA of this microbe was of 

 the AT-type and contained 21.1% of guanine, 24.8% of adenine, 25.8% of cytosine, 

 and 28.3% of thymine. The RNA contained 31.5% of guanine, 18.0% of adenine, 30.3% 

 of cytosine, and 20.2% of uracil. 



Another group of data on experimental variability concerns less marked deviations 

 from the original forms, i.e., the variability of a single marker and not that of a large 

 complex of characters. These data are intimately connected with those on strain 

 differences in microbes (cf. above). The most illustrative data in this respect are 

 those obtained by means of comparing the nucleic acid composition in forms resist- 

 ant or sensitive to antibiotics. Dutta, Jones, and Stacey 132 studied the DNA and 

 RNA composition in the original strain of S. lutea which is sensitive to streptomycin, 

 and in a resistant strain produced from the original one. It was found that the DNA 

 did not alter in composition, whereas small, but statistically reliable, differences 

 were found for RNA (cf. Table IX). The DNA and RNA composition in A. aerogenes 

 — in the original strain and in a streptomycin-resistant one produced from it — were 

 also studied. 151 Here, the DNA composition shows only a small shift (cf. Table II), 

 whereas no considerable alterations were found in the RNA composition (cf. Table 

 VIII). 



Studying slimy and dull variants of Azotobacter chroococcum, Belozersky, Im- 

 senecki et al. 113 found no differences in either DNA (Table I) or RNA (Table VIII). 



The data presented in this section on the nucleic acid composition of 

 bacteria in different types of variability show a complicated and unequal 

 picture. It should be recognized that these data are insufficient for any 



172 R. J. Lynn and P. F. Smith, J. Bacteriol. 74, 811 (1957). 



173 A. N. Belozersky, A. A. Imsenecki, G. N. Zaitseva, and K. S. Perova, Mikrobio- 

 logia 27, 150 (1958). 



