ADSORPTION OF PHAGE TO HOST CELL 149 



tial for the reversible adsorption to host cells (Garen and Puck, 

 1951). As mentioned previously, the same is true of the ad- 

 sorption to glass. 



Stent and Wollman (1952) found that the rate of irreversible 

 adsorption of T4 decreases with decreasing temperature in the 

 range from 25 to 5 ° C. The rate constant also depends on bac- 

 terial concentration, decreasing at concentrations in excess of 

 10^ per ml. They considered three hypotheses to account for 

 these characteristics. 



7. A reversible equilibrium exists between two states of the 

 phage particle, an active state capable of adsorption, and an 

 inacUve state which cannot adsorb. The equilibrium would be 

 temperature dependent. 



2. Adsorption may occur by two competing reactions, revers- 

 ible and irreversible. At high bacterial concentrations, most 

 of the phage is adsorbed reversibly and the rate of desorption 

 controls the rate of irreversible adsorption. 



.3. Adsoiption necessarily involves an initial, reversible at- 

 tachment. Reversibly adsorbed phage may desorb, or become 

 irreversibly attached, by competing reactions. At high bacterial 

 concentrations and especially at low temperatures the conversion 

 from reversible to irreversible attachment, dependent on tem- 

 perature, becomes rate-limiting. 



The third hypothesis is the same as that of Garen and Puck 

 (1951). The infection of host cell (B) by phage (P) may be ex- 

 pressed as: 



k^ k3 



P + B . PB > X 



ki 



where X represents the irreversibly infected host cell. The ve- 

 locity constant ki is the rate of primary attachment and has a low 

 temperature coefficient. The constant k^ is the rate at which 

 reversibly attached phage becomes irreversibly fixed to the host 

 cell. This rate has the relatively high temperature coefficient 

 discussed above. The constant Ajo is the rate at which reversibly 

 attached phage is liberated again into the medium. Stent and 

 Wollman using T4, and Garen (1954) using Tl, demonstrated 



