EFFECTS OF RADIATION ON BACTERIA 421 



studies of the genetic and lethal effects seem desirable, whenever possible, 

 in order to determine the extent to which the mechanisms involved in 

 producing these effects are common or distinct. 



Some of the problems which seem worthy of more detailed study are 

 photoreactivation, the indirect and presumed direct effects of X rays, the 

 various types of recovery which have been observed, the differences in 

 response of cells grown under different conditions, and chemical protec- 

 tion. Additional investigations of the physiological properties of irra- 

 diated cells may help to determine the nature of the ultimate lethal dam- 

 age produced by irradiation. Even the kinetic picture is not clear, and 

 studies of inactivation (e.g., Stapleton, 1952) and parallel studies of kill- 

 ing and mutation (e.g., Witkin, 1951), both of which take into account 

 the nuclear constitution of the cells, seem especially valuable. 



Although much has been learned, especially during the past decade, 

 concerning radiation effects on bacteria and the mechanisms whereby they 

 are produced, the advances in the immediate future seem likely to far sur- 

 pass those of the past, for there have never been so many promising 

 approaches from different directions utilizing such critical techniques as 

 are now available. 



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Allen, A. O. (1948) Radiation chemistry of aqueous solutions. J. Phys. Colloid 

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Anderson, E. H. (1946) Growth requirements of virus-resistant mutants of Escher- 

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