M. Schlesinger 



for living bacteria. The distribution of bacteriophages in a mixture of living and 

 dead bacteria is presented in Table III. 



Table III 



The results of this method are thus in agreement with those obtained from the 

 first method. Hence adsorption of phages to young living bacteria proceeds 2 to 

 3 times more rapidly than adsorption to dead bacteria. If we multiply the value 

 of k of 1.3 X 10~^\ determined in numerous experiments with dead bacteria, by 

 the proportionality constant 2.6, we obtain the velocity constant of adsorption to 

 living bacteria: k = 3.4 X 10~^^ 



Determination of the Saturation Capacity of Bacteria. 



The following method was selected for determining the maximum number of 

 bacteriophages, referred to as the saturation capacity of the bacterium, that the 

 average heat-killed bacterium can adsorb: samples are prepared which contain 

 exactly the same number of dead bacteria but to which increasing initial concen- 

 trations of bacteriophages are added. After a sufficient length of time has 

 elapsed, all of the free bacteriophages capable of irreversible adsorption will have 

 disappeared from each sample. The remaining phage titer will thus be independ- 

 ent of the absolute value of the initial phage concentration, or, at any rate, will 

 represent only a small fraction of it. In fact, the approximate constancy of the 

 relative decrease in free phage should persist even when the allowed reaction time 

 is insufficient for the attainment of the final state; for both parameters im- 

 portant for the velocity of adsorption, the concentration of the bacteria and the 

 relative proportion of phages of differing adsorbability, are constant for all of the 

 samples. This picture will change, however, and change drastically, whenever 

 the initial concentration of bacteriophages attains that multiple of the bacterial 

 concentration which corresponds to the saturation capacity. For instance, when 

 the initial concentration is only half of the saturation capacity, then the adsorp- 

 tion velocity could be reduced, but only near the end of the adsorption process; 

 when, however, the initial concentration of phage is twice that of the total 

 bacterial capacity, then irrespective of the length of time of the experiment, only 

 half of the initial phage population can be adsorbed. The saturation range thus 

 manifests itself by a rapid increase in the ratio of final to initial phage titer in such 

 an adsorption experiment. This ratio will vary from a value of about 0.01 prior 

 to a saturating phage concentration to a value of about 1.0, once saturation has 



30 



