THE ACTION OF RADIATIONS ON VIRUSES 



AND BACTERIA 



D. E. LEA, M.A., Ph.D. 

 Strangeways Research Laboratory, Cambridge 



Introduction 



THE viruses are parasites of bacteria, plants, or animals, 

 characterized by their small size and their inability to 

 multiply except in or on the living cells of the appropriate 

 host. The larger viruses, such as vaccinia, are probably cor- 

 rectly regarded as single-celled organisms. The smallest viruses 

 are nucleoproteins, capable of being concentrated and purified 

 by the methods of protein chemistry, and in some cases obtain- 

 able in a crystalline form. It is evidently not correct to regard' 

 these small viruses as cells. From a biological standpoint, they 

 may be thought of as naked genes. ^^ From a chemical stand- 

 point, they are to be thought of as large molecules (macromole- 

 cules) of molecular weight 1 to 100 millions. 



Thus, one may expect to find analogies between the mechanism 

 of action of radiations on viruses (at any rate in the case of 

 the smallest viruses), and chemical effects of radiation, and we 

 shall therefore recall the outstanding conclusions of the study 

 of the chemical effects of radiation. \' '^ 



Chemical Effects of Radiation 



If a chemical substance is irradiated in the pure state by 

 X-rays or alpha rays, the typical result is that approximately 

 one molecule is decomposed for each ionization produced. It 

 appears that the ionization of an atom usually leads to the 

 decomposition of the molecule of which it is a part, a result 



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