CYTOLOGICAL CHANCES DURING GERMINATION 



87 



I 



O 

 O Q. 



15 



10 



I 5 - 



9f> 



50 



100 



150 200 



mg. DNA-P/IOOg. SPORES 



Fig. 2. The relation between basophilic nuclear material (chromatin) and 

 DNA-P during the rapid germination of B. cereus. 



showed no nucleic acid synthesis but only a rise in acid-soluble phosphorus 

 concomitant with a fall in phosphorous of the residue fraction. The two 

 points I wish to bring up here are the change in rate of RNA synthesis 

 which occurred just as or before the desoxyribose nucleic acid (DNA) be- 

 gan to rise and the steady rise in DNA-P. The break in the rate of RNA 

 synthesis was found in all experiments in which germination and growth 

 was sufi&ciently synchronous and could be used as an indication of syn- 

 chrony. Even the most synchronous studies however always showed a steady 

 rise in DNA. This rise in DNA was found to be proportional to the amount 

 of stainable chromatin estimated by the technique of projecting and tracing 

 microphotographs and weighing the paper images of the chromatin (Fig. 

 2). During the period of study chosen the amount of DNA found in the 

 spore had doubled and the number of nuclear bodies had increased accord- 

 ingly (Fig. 3). 



This indicated that the nuclear body of the bacillary cell tended to have 

 a constant DNA content and that during germination reduplication and divi- 

 sion went on at the same time and was complete when the original amount 

 of DNA had been doubled. It also suggests that the spore contains the small- 

 est functioning amount of DNA and indicates to me the biological goal of 

 a sporulating cell — to parcel in an insulated chamber the functioning unil 

 of chromatin. 



Some more recent studies conducted jointly with Miss Young have per- 

 mitted further examination of the average concentration of DNA/spore of 

 a number of species and indicated the influence common laboratory media 

 might have on the nucleic acid content as well as on the size of the spore. 



