SYLLABUS 121 



are dissolved by the phages. The membranes disintegrate into granular 

 material. 



A similar material, isolated by the same procedure from a B-mu- 

 tant sensitive to T2 only, inactivates only T2 phages. 



Chemistry 



The bacterial membranes are built from an astonishingly resistant 

 material. For example, organic solvents, low or high pH, saturated 

 urea solutions and trichloroacetic acid, drying in the desiccator, have no 

 damaging effect upon their macroscopic appearance or upon their anti- 

 phage activity. Hydrolysis with concentrated HCl at room temperature 

 for several days yields a mixture of amino acids, a completely insoluble 

 substance, as yet undefined, and a lipid fraction consisting of a neutral 

 oil and a mixture of fatty acids, one of which is crystallized. The 

 sodium salts of these acids gelatinize in water solution at high dilution. 

 No reducing sugars could be detected in the hydrolysate, and no humin 

 was formed during hydrolysis. Elementary analysis indicated the 

 presence of about .5% phosphorous. Analysis from different prepara- 

 tions gave only minor fluctuations of the values for C, H, N, and P. 

 From these data, which still have to be completed, one might draw the 

 conclusion that the cell wall of coli B or a certain well defined layer of 

 it consists of a phospholipoproteid of unusual properties. It has often 

 been claimed that polysaccharide compounds of bacterial cell walls 

 play a main role in specific adsorption of bacteriophages to their host. 

 The results of this work do not support this assumption for E. coli B. 



A somatic antigen of Sh. sonnei was isolated and showed specific 

 activity against T3, T4, and T7 (Miller and Goebel, 1949), but the 

 pure substance was found to be almost inactive after a few months. 

 Chemically it is a lipocarbohydrate-protein complex. It seems that bac- 

 terial antigenic polysaccharides serve as the specific sites in many cases 

 (Pirie, 1940). 



IV. Invasion 



18. In the preceding section we have seen that the specific com- 

 bination of phage with its receptor spot does not harm the bacterium. 

 The next phase that we can distinguish kills the bacterium. This stage 

 is defined, as is the previous one, by certain freak situations in which 

 progress beyond it is made impossible. We call this the stage of invasion. 



19. Characteristics of invasion. — At this stage new infective par- 

 ticles have not yet been produced, nor will there be any produced if 

 progress is arrested. On the other hand, the infecting particle is lost 



