152 A. N. BELOZERSKY AND A. S. SPIRIN 



decrease in accordance with the decreased multiplication rate of the cells 

 in culture, and, correspondingly, with the rate of protein synthesis. The 

 maximal RNA amount is found during the period of most intensive growth 

 or just prior to this period. In the periods during which the multiplication 

 rate of the cells is constant, the RNA content per cell is also approximately 

 constant. 



The direct connection between the RNA content per cell and the rate of 

 growth, multiplication, and protein synthesis was shown, also, in studies 

 with cultures in which different rates of synthesis and growth were achieved 

 through changes in the medium, 12 ' 21 > 49 " 52 by various inhibitors, 12 ' 21, 51, 53 

 and also by studying mutants and strains possessing different rates of 

 growth. 12 ' 43 The RNA amount per cell was shown to be directly propor- 

 ional to the reciprocal of the average generation time, i.e., to the rate of 

 cell multiplication. 12 It was noted that the RNA content in the cells con- 

 trols the rate of growth and protein synthesis, 21 and that at the constant 

 rate of multiplication in steady-state systems, there exists an exact correla- 

 tion between the rate of protein synthesis and the RNA amount which is 

 excessive with respect to the constant basic amount that is always present 

 in the cell. 50 Of recent studies, data on the thermophilic bacteria are of 

 interest, in which the cells contained the maximal RNA amount at tem- 

 peratures optimal for their multiplication. 54 German authors 54 ' 57 showed 

 that during the inhibition of the growth of microorganisms by metal ions, 

 temperature, and other agents, a decrease of the RNA content and an 

 increase of the DNA/RNA ratio takes place. In this connection, the work 

 of Russian authors 46 ' 47 should be mentioned in which a study of the RNA 

 content in the original bacteria and in variants produced under the influence 

 of antibiotics was carried out. Here, a lower rate of growth and multiplica- 

 tion of the cells and a more prolonged cycle of growth in modified variants 

 were accompanied by a low level of RNA content. 



Thus, the presence of a definite level of RNA content in the microbial 

 cells seems to ensure a corresponding rate of growth and multiplication of 

 cells in the culture. 



Valuable material, in this respect, is given by the study of the lag-phase 



49 F. J. DiCarlo and A. S. Shultz, Arch. Biochem. 17, 293 (1948). 

 60 R. Jeener, Arch. Biochem. Biophys. 43, 381 (1953). 



51 E. F. Gale, 2nd Intern. Congr. Biochem. Paris "Symp. sur le mode d'action des 

 antibiotiques," p. 5 (1952). 



52 E. F. Gale and J. P. Folkes, Biochem. J. 53, 483 (1953). 



53 E. F. Gale and J. P. Folkes, Biochem. J. 53, 493 (1953). 



54 R. Wellerson and P. A. Tetrault, J. Bacteriol. 69, 449 (1955). 



55 O. Kandler, J. Muller, and C. Zehender, Arch. Mikrobiol. 24, 250 (1956). 



56 A. Rippel-Baldes, G. Busch, and F. Radler, Arch. Mikrobiol. 23, 423 (1956). 



57 E. Petras, Arch. Mikrobiol. 30, 147 (1958). 



