17 



The Effect of X Rays on the Incorporation 

 of Phosphorus and Sulfur into Escherichia colt 



ERNEST POLLARD JANE KENNEDY 



Biophysics Department^ Yale University 



In the previous paper of this volume an account was given of preliminary 

 studies on the effect of ionizing radiation on the incorporation of amino acids 

 and glucose into a fraction of the bacterial cell that is not soluble in trichloro- 

 acetic acid. It is hoped that a continuation of such probing into the synthetic 

 processes in the cell by radiation will give some information on the nature of 

 the processes themselves. Though the subject of keenest interest at the moment 

 is undoubtedly the fate of an individual metabolite, and the way in which it 

 becomes incorporated, it seemed to be important to know something of the 

 way in which radiation affects the uptake of two much more generally utilized 

 elements of the growth medium, phosphate and sulfate. The studies to be de- 

 scribed were originally meant simply as a means of gaining general informa- 

 tion about the effect of radiation on the cell metabolism, to ensure that no seri- 

 ous discrepancies existed between the findings with one amino acid and the 

 whole metabolic process of the cell. During the studies some results appeared 

 that seem to indicate rather remarkable radiation sensitivities and are, more- 

 over, of interest in themselves. For instance, the ability of the cell to incor- 

 porate phosphate is remarkably sensitive to X radiation; the sulfate-incorpora- 

 tion ability is also highly sensitive, though less so; and sulfide incorporation is 

 definitely still less sensitive. The hypothesis that suggests itself is that the 

 phosphorus incorporation is determined by relatively large and sensitive units, 

 and that when these are damaged by radiation there is a proportionally smaller 

 phosphorus uptake. For sulfur uptake the results are in accord with the idea 

 that there is a considerable synthetic chain which presents sensitivity at a num- 



1 Aided by a grant from the United States Public Health Service. 



136 



