THE SYNTHESIS OF PROTEINS 29 



ally be the only one which takes place. If Pg -^ V2, therefore, is more 

 rapid than P2 -^ Vi, the virus finally produced will be practically pure 

 V2, the length of time required depending on the relative reaction rates. 



An example of such a transformation is furnished by Gratia's in- 

 teresting results (1936) with B. megatherium. This organism exists in 

 two forms, "lysogenic" and "sensitive." The lysogenic strain constantly 

 produces a virus T, which does not cause lysis of the parent lysogenic 

 strain but does cause lysis of the sensitive strain. Subculture of plaques 

 of this virus on the sensitive strain gives rise to two different viruses, 

 the original T and a new one, C, which causes lysis of both strains. 

 Similar results have been reported by Luria (1945). 



It does not appear possible to make any generalization on theoretical 

 grounds as to whether or not the products of an "autocatalytic" reaction 

 are identical with the original catalyst. The hydrolysis of esters by acids 

 is an autocatalytic reaction and may give rise either to more of the same 

 acid or to different acids, depending on conditions. Thus the hydrolysis 

 of ethyl acetate, propyl acetate, and butyl acetate by means of acetic 

 acid will result in the formation of more acetic acid ; but the hydrolysis 

 of ethyl butyrate and ethyl propionate by acetic acid will result in the 

 production of butyric and propionic acids. Although hydrolysis is 

 caused primarily in this case by the hydrogen ion, which is the same in 

 all acids, the same relation holds presumably for proteins ; the ability 

 to produce certain reactions is primarily a property of certain groups 

 and these groups may be common to many different proteins. 



Quantitative Data on the Formation of Bacterial Viruses 

 (Bacteriophages). If viruses are formed from precursors in the cell 

 it follows that the quantity of virus formed in any one cell should be 

 constant, provided no increase in the precursor occurs during the re- 

 action. Viruses in general, and bacterial viruses in particular, increase 

 most rapidly in the presence of growing host cells ; and under these 

 conditions the number of infected host cells is constantly changing and 

 more precursor is presumably being formed so that the amount of virus 

 formed per host cell cannot be determined. Krueger and his collaborators 

 (cf. Krueger and Scribner, 1939) found that bacteria viruses could be 

 produced under certain conditions without cell growth, and Krueger and 

 Baldwin (1937) obtained occasional virus increase in cell-free solution. 

 Krueger concluded that the virus was produced from a precursor in the 

 bacterial cell. Spizizen (1943) reports virus production in dilute solu- 

 tions of glycine anhydride without cell growth. Delbriick and Luria 

 separated virus production from cell growth by dilution of the culture 



