1 98 BACTERIOPHAGES 



the cytological changes were the same as those observed with 

 active Tl except that lysis did not occur. With inactivated T7 

 phage the initial changes were the same as with active T7 phage, 

 but then the cells filled up with chromatin like Tl -infected cells 

 instead of forming a large central chromatinic body as was seen 

 with active T7 phage. In the case of infection with irradiated 

 Tl phage, synthesis of material absorbing at 2,600 A proceeded 

 at the same rate as with active phage, but with irradiated T2 

 phage the synthesis of light-absorbing material proceeded at a 

 relatively slow rate compared with synthesis in bacteria infected 

 with active phage T2. Heden (1951) reported that his cytolog- 

 ical studies with T2-infected E. coli cells were in essential agree- 

 ment with the results of Luria and Human. 



An intensive study of the cytological changes produced in E. 

 coli by infection with phage T2 was made by Murray, Gillen, and 

 Heagy (1950). The staining methods of Robinow were used, 

 and replicate samples of infected bacteria taken at intervals dur- 

 ing the latent period were stained with Giemsa (after treatment 

 with HCl) for chromatin, with thionine for cytoplasm, and with 

 tannic acid and gentian violet for cell walls. The Giemsa and 

 thionine staining methods complemented each other and the cell 

 wall stain permitted the visualization of bacterial "ghosts" after 

 lysis had occurred. The observations with the Giemsa stain 

 were in agreement with those of Luria and Human (1950). 

 During the first few minutes the bacterial nucleus disintegrated 

 and the chromatin migrated to the periphery of the cell forming 

 "marginated cells." Then during the second half of the latent 

 period, this chromatin became granular. In lysis-inhibited cells 

 the granules increased in size and coalesced, giving a banded ap- 

 pearance. The staining capacity of the cytoplasm with thionine 

 decreased and was alm.ost lost at the time of lysis. The authors 

 suggested that late in the latent period the chromatin is distrib- 

 uted cylindrically near the cell wall. This paper is illustrated 

 with beautifully reproduced photographs of stained preparations. 

 Studies of T2-infected bacteria by Beutner, Hartman, Mudd, and 

 Hillier (1953) using DeLamatcr's staining technique are in agree- 

 ment with the results obtained by the previous investigators. 



