"age of culture" effects 81 



and nucleic acids, have a very marked absorption in the ultra- 

 violet at 265 m/x, and changes in the amount of such substances 

 in the cells can be shown by photographing the cells in light 

 of that wave-length. If this is done, it is found that cells from 

 old cultures have very little " nucleic " material but that this 

 increases markedly during the growth phases corresponding to 

 the late lag and early logarithmic periods; the concentration 

 then decreases steadily throughout the phases of negative 

 growth acceleration and stationary growth. The changes in the 

 concentration of nucleic material {i.e. measured by its U-V 

 absorption at 265 m/x) are related to the growth of the organism 

 as shown in Fig. 7. It can be seen that there may well be 

 correlation between these alterations in composition and those 

 variations in enzymic activity described above. 



FOR FURTHER READING 



Genetics of Micro-organisms, Catcheside, D. G. (Pitmans). 



" Enzymatische Adaptation bei Mikroorganismen," 

 Karstrom, H., Ergebnisse de Enzymforschung, 1938, 7, 350. 



" Factors Influencing the Enzymic Activities of Bacteria," 

 Gale, E. F., Bacteriological Reviews, 1943, 7, 139. 



La Croissance des Cultures Bacteriennes, Monod, J., 1943 

 (Hermann et Cie, Paris). 



Original paper: " Studies on the Chemical Nature of the 

 Substances Inducing Transformation of Pneumococcal Types," 

 Avery, 0. T., MacLeod, C. M., and McCarty, M., J. exp. Med., 

 1944, 79, 137. 



CHEM. A. H. 



