32. THE NUCLEIC ACIDS OF MICROORGANISMS 153 



in nonsporulating microorganisms, 20 ' 23, 26. 27. 42, 43, 45, 47. 58 or ^y ^ e i nves . 

 tigation of the germination of spores in sporeforming species. 25, 28, 40 ' 59 Dur- 

 ing this early period of development, prior to cellular division, an intensive 

 RNA synthesis takes place in the cells. According to some data, RXA syn- 

 thesis precedes that of DNA in the cell; with the onset of DXA synthesis, 

 which takes place just prior to the division, RNA synthesis slows down some- 

 what. 25, 26, 40, 45 Protein synthesis in the cell begins, also, only when a cer- 

 tain level of RXA content is achieved, so that RXA accumulation always 

 precedes protein synthesis in the lag-phase or during the germination of 

 spores. It is typical that during the lag-phase the nucleic acid synthesis 

 takes precedence over protein synthesis, whereas in the absence of ni- 

 trogen uptake from the medium the former can proceed at the expense 

 of protein. 23 Moreover, even in the case of nitrogen uptake from the 

 medium, there takes place, during this period, a redistribution of nitrogen 

 in the cells, so that, the nucleic acids do not utilize the nitrogen of the 

 medium but that of cellular constituents, presumably, of proteins. 27 In the 

 case of the germination of Bacillus cere us spores, the nucleic acid synthesis 

 began only when the germinated spores were placed in a nutritive medium. 28 



The same regularities, namely an intensive RXA accumulation preceding 

 intensive growth of mycelium, were found in early phases of the growth of 

 Actinomycetes when the inoculum was transferred to large fermenters. 39 

 Here, RXA synthesis also preceded that of DNA. 



The regularities revealed in the study of the lag-phase and subsequent 

 cellular division are completely confirmed when synchronous cultures of 

 microorganisms are studied. 30 " 32, 34 Here, the RXA content of the cells also 

 increases very rapidly attaining its maximum by the onset of intensive 

 protein synthesis; thereafter, RXA synthesis in the cell slows down, and 

 then, with the onset of cellular division, proceeds proportionally to the 

 multiplication of the cells. Unlike DXA, which is synthesized only imme- 

 diately before the division of the cells, RXA synthesis proceeds in the 

 culture more or less continuously. 



Thus, the necessity of a latent period seems to be due to the fact that it 

 is this "starting" period, when an accumulation of RXA occurs in the cell 

 up to a certain level, which ensures a corresponding rate of protein synthesis, 

 growth, and multiplication. 



During the subsequent period of logarithmic growth, a direct correlation 

 is observed, as a rule, between the RXA content in the cells and the rate of 

 both growth and protein synthesis. RXA and protein synthesis proceeds 

 more or less in parallel, slowing down gradually. 



58 T. Brechbiihler, Bull. soc. chim. biol. 32, 952 (1950; . 

 89 T. Yanagita, Arch. Mikrobiol. 26, 329 (1957). 



