DAMAGE IN AEROBIC AND ANAEROBIC SYSTEMS 41 



diflferent chemical pathways is equally reparable by a given form of 

 metabolic control. There is now abundant evidence to show that it is 

 not. An extreme example comes from recent observations of Laser 

 (1960) that starvation oi Pseudomonas for 48 lir after irradiation com- 

 pletely eliminates damage which is oxygen dependent, but leaves un- 

 changed the damage which does not involve the participation of oxygen 

 in the chemical chain. 



Alper and Gillies (1958; 1960a, b) have recently made a special study 

 of this problem using loss of reproductive integrity in E. coli B, irradi- 

 ated aerobically and anaerobically, as test material for the influence of 

 post-irradiation nutritional factors, Alper (1961) finds that the ratio of 

 the sensitivity of organisms irradiated in oxygen and in nitrogen (i.e. 

 the constant m of equation (1)) is approximately linearly related to the 

 value of Do observed for organisms that have been irradiated anoxically , 

 irrespective of the culture condition used to control Dq. Alper estimates 

 that whereas m = 3-6 under conditions that give maximum injury (no 

 "restoration") m = 1-5 under conditions that give minimum injury 

 (full "restoration"). 



In other organisms m may be unaffected by the conditions of culture. 

 The more usual case, however, appears to be of the kind investigated 

 by Alper and Gillies, and we have to consider that chemical control and 

 metabolic control are interrelated variables as regards radiation induced 

 loss of reproductive integrity. 



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