140 BACTERIOPHAGES 



terium. Delbriick (1940a) using a different coliphage and a 

 different strain of E. coli found that the saturation value for a 

 culture in the logarithmic growth phase was 250 phage per bac- 

 terium, and Watson (1950) found a maximum value of 300 phage 

 per bacterium for the adsorption of T2 to heat-killed E. coli 

 strain B. 



Schlesinger (1932c) adapted the coagulation theory of von 

 Smoluchowski to the kinetics of phage adsorption, and derived 

 the equation : 



-dP/dt = AttDRBP (3) 



in which —dP/dt is the rate of adsorption, D is the diffusion con- 

 stant of the phage particle, R is the radius of a sphere of the 

 same surface area as the bacterium, and the other symbols are 

 as in equation (1). By combining equations (1) and (3) he 

 ohtained the equation 



k = AttDR (4) 



Equation (4) contains the assumptions that every collision 

 between phage and bacterium results in irreversible adsorption, 

 that the bacteria and surrounding fluid are stationary, and that 

 the phage particle itself is dimensionless. In spite of obvious 

 defects, it gives a rough estimate of what the maximum possible 

 rate of adsorption ought to be. 



Schlesinger calculated the diffusion constant from his observed 

 adsorption-rate constant by means of equation (4) : 



3.4 X 10-" 



6.3 X 10-'* cm.- sec. -1 



At X 4.3 X 10-^ 



According to Taylor, Epstein, and Lauffer (1955), the diffusion 

 coefficient of phages T2 and T6, related to WLL, is about 3.5 X 

 10-^ cm. 2 sec.-^ at 20° C, in reasonable agreement with 

 Schlesinger's indirect measurement at 37 ° C. This means that 

 the observed adsorption-rate constant of equation (2) is in agree- 

 ment with the theory represented by equation (4), as found also 

 by Delbriick (1940a), Puck, Garen, and Cline (1951), and Stent 



