210 A. GAEEN AND L. M. KOZLOFF 



phage-neutralizing antibody, as indicated botli by the lack of neutralizing anti- 

 body in antiserum made from heads and by the inability of purified prepara- 

 tions of heads to react with neutraHzing antibody. Furthermore, T2 particles 

 that have lost their tail fibers and the distal portion of their tail core after 

 treatment "with zinc cyanide complexes also lose the capacity to react with 

 neutralizing antibody (Kozloff et al., 1957), which suggests that the tail 

 antigen is located in the distal portion of the tail. Particles neutralized by 

 anti-T2 serum retain the capacity to attach to cells but are unable to kill or to 

 inject their DNA (Nagano et al, 1952; Nagano and Oda, 1955; Tolmach, 1957). 

 The presence of a head antigen has been detected by complement fixation 

 tests with purified head material (Lanni and Lanni, 1953). It is not known if 

 this antigen is restricted to the head or is also present in the tail. A new com- 

 plement-fixing activity (without neutralizing activity) has recently been 

 discovered in antiserum made from the material released from T2 by 

 osmotic shock (Levine et al., 1957). The component responsible for this 

 serological activity is a basic protein; its relationship to other phage com- 

 ponents has not yet been determined. 



III. The Bacterial Surface 



Recent studies of the exterior surface of bacterial cells have provided 

 important information about its organization and chemical composition and 

 about the pathways for its synthesis (Work, 1957). The surface structure, or 

 wall, has been isolated as a separate component from several bacterial strains 

 after mechanical rupture or chemical treatment of the cell (Salton and Home, 

 1951; Weidel et al. 1954). Purified walls appear in electron micrographs as 

 empty casings, 100-200 A in thickness, with contours characteristic of the 

 intact cell (Salton and Williams, 1954). This structure, therefore, must have 

 considerable rigidity. Walls prepared by the above procedures retain the 

 capacity of the intact cell to bind certain phages (Weidel et al., 1954; Salton, 

 1956). These preparations are chemically complex, containing lipid, sugars, 

 and many amino acids (Work, 1957). Alanine and glutamic acid are usually 

 present in the d as well as the l form, and in certain strains a new amino 

 acid, diaminopimelic acid, replaces some of the lysine. 



The surfaces of some bacterial strains are encapsulated by highly poly- 

 merized polysaccharide material. It has been fomid that a phage capable of 

 infecting these cells either contains, or elicits the synthesis of, a hydrolytic 

 enzyme for the capsular material (Adams and Park, 1956). 



The cell surface also contains an inner layer, or membrane, as revealed in 

 two different ways: by treating intact cells either with lysozyme, which 

 degrades the waU (Weibull, 1953a; Zinder and Arndt, 1956), or with peni- 

 cillin, which appears to block the synthesis of new wall material (Lederberg, 

 1956, 1957; Park and Strominger, 1957). Both treatments, when carried out 



