CYTOLOGICAL CHANGES IN THE INFECTED HOST CELL 203 



rapid decompression technique of Fraser (1951b) was used by 

 Levinthal and Fisher (1952, 1953) (Chapler XI). Phage-in- 

 fected bacteria are unusually fragile and may be easily ruptured 

 (Levinthal and Visconti, 1953). This undoubtedly accounts for 

 the claim by Wyckoff (1949a) that phage-infected bacteria lyse, 

 in the sense of cell rupture, within 5 minutes after infection. 

 Wyckoff concluded "that the membranes of young bacteria rup- 

 ture soon after contact with phage which then proliferates in and 

 at the expense of the bacterial protoplasm by a process that re- 

 sembles the division shown by bacteria and other microorgan- 

 isms." This conclusion is at variance with all other evidence 

 about phage multiplication. 



Useful information can be obtained from experiments with iso- 

 lated host cell components, as was the case in Weidel's (1951) 

 study of the effect of the T-even phages upon isolated cell mem- 

 branes of E. coli B (see also Chapter XI). He showed that a 

 local damage to the cell wall occurred after adsorption had taken 

 place. The local loosening of the wall fabric was recognizable 

 as visibly altered patches of the wall and, if a sufficient number 

 of particles were adsorbed, could result in complete destruction. 

 His description of the phases of destruction is very reminiscent of 

 the previously noted descriptions of "lysis from without." 



Another method for studying whole phage-infected bacteria in 

 the electron microscope employs a high contrast lens system, 

 which permits some differentiation of structure to be observed 

 even in uninfected cells (Mudd, Hillier, Beutner, and Hartman, 

 1953). In cultures of E. coli typical cells have three opaque 

 areas, at the two poles and in the center of the cell. These 

 opaque, cytoplasmic regions are separated by areas of lesser 

 density corresponding to the two nuclear bodies as seen in stained 

 cells and to the "vacuoles" seen in sectioned bacteria by Birch- 

 Andersen, Maal0e, and Sjostrand (1953). Some minutes after 

 infection with phage T2, the less dense areas move to the margins 

 of the cells, much as does the chromatin seen in stained prepara- 

 tions. For the first half of the latent period there is no evidence 

 of any intracellular objects resembling mature phage. During 



