256 



W. KUNICKI-GOLDFINGER 



in buffer is shown in Table IV. The synchronization of growth 

 w^as not quite unexpected, as there is ample evidence of the 

 effects of starvation and variation in temperature on this 

 process (Scherbaum and Zeuthen, 1954; Lark and Maal0e, 

 1954; Hotchkiss, 1954; Earner and Cohen, 1955; Hunter- 

 Szybalska, Szybalski and DeLamater, 1956; Maruyama and 

 Yanagita, 1956). 



Table IV 



Synchronization of growth of Esch. coli after starvation 

 AND cooling 



What is the mechanism of the development of streptomycin 

 resistance in bacteria in the above experiments? Induced 

 mutation in a total population may seem to have been 

 excluded. The results obtained, i.e. absence of specifically 

 inducing agent and the conditions unfavourable for growth 

 and synthesis of cell material, suggest that the "automatic 

 adjustment" of Hinshelwood (1946, 1953) is not operating in 

 this case. 



The synchronous growth is probably accompanied by tran- 

 sient polyploidy. The normal cytological pattern of the cells 

 is, howxver, restored much earlier than the streptomycin- 

 sensitivity state. Polyploidy could be then only a contri- 

 buting factor, operating in the early stages of phenotypic 

 change. 



It is perhaps relevant here to recall some examples of con- 

 verting a large percentage of microbial cells by treatments 



