200 BACTERIOPHAGES 



Bonifas and Kellenberger (1955) observed that adsorption of 

 ghosts of phage T2 caused an aggregation of the host cell chroma- 

 tin rather than the peripheral migration observed when either 

 active or ultraviolet-inactivated phage was adsorbed. This was 

 confirmed by Whitfield and Murray (1957) who further ob- 

 served that if the multiplicity of infection with the active phage 

 was increased to 70 or 100 phage per cell chromatin aggrega- 

 tion preceded the premature "lysis from without." Multiple 

 infection with T5 phage likewise caused aggregation to precede 

 the usual loss of stain able chromatin. The above observations 

 suggest that alterations of the cell boundary, more severe follow- 

 ing infection with ghosts than with phage, contribute to cytologi- 

 cal effects. 



Puck and Lee (1954, 1955) suggested that infection with any 

 of the T phages initiates a cycle of permeability changes in the 

 cell boundary during the period following the attachment of the 

 phage to the cell. Direct evidence of visible as well as chemical 

 disorganization of cell membranes by phage adsorption has also 

 been noted (Chapter XI). The studies of Whitfield and Murray 

 (1956, 1957) showed that some of the cytological effects of infec- 

 tion may be secondary to permeability changes. They found 

 that the chromatin aggregation, so commonly observed as a 

 first cytological stage of infection (e.g., with phage T7), occurred 

 at low multiplicities of infection if a sufficient quantity of sodium 

 chloride was present in the medium; on salt-deficient medium 

 this effect was replaced by chromatin fragmentation. With 

 phages T2 and T5 the same was true, provided that there was a 

 sufficient multiplicity of infection. The results suggest that the 

 conformation of chromatin is dependent on the ionic balance 

 maintained in the living cell; disturbance of this balance, 

 whether by phage adsorption to the cell surface or by metabolic 

 interference, is reflected in the subsequent behavior of chroma- 

 tin, which varies according to the cationic environment provided 

 for the experiment. These considerations underline the cau- 

 tions expressed at the beginning of this chapter. 



Lysogenic systems have not been subjected to much cytological 



