A study of bacterial populations with induced nuclear and cellular divisions 



Birch-Andersen, A., Maalce, O. and Sjostrand, F. S. (1953). High-resolution 

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Boyd, J. S. K. (1950). The symbiotic bacteriophages of Salmonella typhimurium. J. 

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DeLamater, E. D. (1952). A consideration of the newer methods for the demonstra- 

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358. 

 Hotchkiss, R. D. (1954). Cyclical behaviour in pneumococcal growth and trans- 



formability occasioned by environmental changes. Proc. nat. Acad. Sci., 40, 49. 

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bacteria. Cold Spr. Harb. Symp. Quant. Biol. 18, 101. 

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 Lederberg, E. M. and Lederberg, J. (1953). Genetic studies of lysogenicity in 



Escherichia coli. Genetics 38, 5 1 . 

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Salmonella typhimurium. Ann. Inst. Pasteur. 86, 127. 

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gresso Interna zionale di Microbiologia, Roma 2, 551. 

 Scherbaum, O. and Zeuthen, E. (1954). Induction of synchronized cell division 



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Discussion 

 Chairman: J. F. Danielli 



K. E. Cooper. Does the resistance of these cultures to antibiotics change in their differ- 

 ent phases ? We have found a critical time in the development of staphylococci on 

 solid media at about four generations after pouring inoculated plates to test anti- 

 biotic action (1952, J. gen. Microbiol. 7, 1-17). A temporary increase in resistance 

 occurs, and may be related to the time required to form some cellular substance 

 after the act of inoculation. 



0. Maaloe. Unfortunately we have no information as yet as to whether bacteria are 

 particularly susceptible to antibiotics at certain points of the division cycle. 



C. Darlington. With regard to the suggested high temperature coefficient of DNA 

 synthesis, in those flowering plants in which mitosis takes place at freezing-point, a 

 starvation of DNA often occurs at specific points in the chromosomes, the segments of 

 heterochromatin, when the temperature is applied for some time before metaphase. 



M. M. Swann. Unlike what happens in plants and animals, there is a considerable 

 separation in your organisms between nuclear division and cell division. However, 

 the partition is laid down earlier, and the 'cell division' appears to be a separation 

 of what are already functionally distinct units. Perhaps then we may regard cyto- 

 plasmic division even in this case as essentially following immediately after nuclear 

 division. 



169 



