VII. THE MODE OF VIRUS MULTIPLICATION 89 



number of salts of carboxylic acids, peptone, and culture broths. 

 Mixtures of equal parts of NaCl and KCL and low concentrations of 

 Na azide and 2.4-dinitrophenol, respectively, were found to exert a 

 pronounced inhibitory effect in this process (103). 



Thus young growing cells seem to have peculiar protoplasm 

 structure which is fitted for phage production, and accordingly if 

 phage was present in bacterial cultures growing rapidly, as soon as 

 the protoplasm proteins were synthesized from the components in the 

 culture medium, the newly formed proteins would be changed into the 

 phage proteins by the rearrangement of the polar groups, so that the 

 components would seem to be converted directly into phage. 



On the other hand, it is believed that bacteria are deprived of 

 their viability by the infection with phage. If this were true, the 

 components in the medium would have failed to enter the bacterial 

 cells after the infection, and hence phage itself would have to take 

 the components if these were found in the phage. However, this 

 assumption is not correct, because the loss of the viability occurs only 

 when bacteria are affected by a phage on an agar plate. In broth 

 culture it seems not to take place at least in a manner so striking as 

 on plate and moreover even on an agar plate only a peculiar phage 

 can reveal the growth-inhibiting property, which is therefore not es- 

 sential for phage. The phage particles isolated and purified by our 

 method always fail to develop the growth-inhibiting property even 

 when it can exhibit the property before the purification. This interest- 

 ing fact is discussed in detail in the other book (22). 



As described in Chapter VI in Part I, the activity of phage varies 

 with the conditions under which the host bacteria are cultivated. The 

 viability and the degree of lysis of bacteria after the infection by 

 phage vary in a similar way. Thus, bacteria may lose the viability 

 when infected with some phage on an agar plate as just mentioned, 

 while this is not the case in a broth culture. In additon, on an agar 

 plate bacteria affected by phage usually undergo a complete lysis while 

 in a broth this does not necessarily follow. For example, according 

 to our observation a certain strain of E. colt fails to undergo lysis in 

 broth by the infection with a strain of phage. The difference be- 

 tween agar and broth culture may be ascribed to the degree of contact 

 with air during the phage inlection, since in the case of broth cul- 

 ture the greater the surface area of the culture, phage multiplies the 

 more rapidly and abundantly (91). The plaque-formation would never 

 result if the lysis and the growth inhibition failed to occur on an 

 agar plate. 



The fact that phage in broth may not only fail to inhibit the 

 grovrth of bacteria but occasionally even can promote it before the 



