SYLLABUS 125 



cell lyses, which does not occur spontaneously until many new particles 

 have been formed. 



Doermann (1948) and Doermann and Anderson (1950) have suc- 

 ceeded in disrupting the cell prematurely by the following methods: 



1) Lysis from without (Delbriick, 1940) : Bacteria infected with T4 

 are metaboUcally inhibited with 5-methyl-tryptophane (Cohen and 

 Fowler, 1947) or cyanide and caused to lyse by means of a high con- 

 centration of T6. Plating is then done on B/6, so that only T4 is 

 measured. 



2) Lysis by addition of cyanide alone, which is effective in the 

 later part of the latent period. 



3) Disruption of infected cells by sonic vibration. T3 is used here, 

 since it is relatively resistant to sonic inactivation (Anderson et al., 

 1948). 



For the first half of the normal latent period, no viable phage is 

 obtained; the original infecting particle is not recovered. Complete new 

 particles begin to appear at roughly half time and the number appear- 

 ing thereafter is a hnear function of time until the maximum yield is 

 reached (see figure 2). 



According to the experiments of Foster (1948), proflavine inhibits 

 a late phase in the synthesis of phage without preventing lysis, so that 

 results similar to Doermann's are obtained by adding proflavine at a 

 given time and allowing the cells to lyse spontaneously. 



28. Fate of the infecting particle. — The infecting particle is lost; 

 it is not present in the yield of the infected bacterium, and apparently 

 the majority of its chemical constituents are not utihzed for building 

 new phage. Three lines of evidence lead to this conclusion: 



A. In mixed infection with the phages Ti and T2, phage Ti is 

 "excluded" (see 31); the mixed-infected bacterium yields only phage 

 T2, and the Ti infecting particle does not appear in the yield (Del- 

 briick and Luria, 1942). 



B. The experiments on premature lysis (see 27) show that during 

 the first one-half of the latent period no particles can be recovered 

 (Doermann, 1948). 



C. If a bacterium is infected with phage labelled with P^^ a frac- 

 tion only of the hot phosphorus present in the infecting particles can be 

 recovered in the yield (Putnam and Kozloff, 1950). (This loss of P of 



