Elie L. Wollman

On the two-step nature of bacteriophage adsorption

Abstract The rate of adsorption of bacteriophages to host cells increases proportionally to the bacterial concentration B at low B and reaches a maximum rate which is independent of B at high B . The fraction of phage-bacterial collisions leading to irreversible union of these two bodies, estimated to be of the order of 0.1 at 15°C, decreases with temperature. Three alternative theories involving a second step besides collision in the mechanism of bacteriophage adsorption are proposed and discussed to account for the experimental observations. One theory envisions the phage particles as oscillating between an “active” and an “inactive” state. The other two theories involve the concept of a reversible attachment of virus to host cell. The half-life of the “active” state or of the reversible attachment is of the order of 15 seconds at 15°C.

Studies on activation of T4 bacteriophage by cofactor. II. The mechanism of activation.

Abstract 1. 1. The rates of activation and deactivation of cofactor-requiring T4 bacteriophages are measured as functions of the tryptophan concentration in the medium. 2. 2. The concept of key-site at which activation of the phage occurs is inferred from the kinetic data and the degree of activity of a phage population defined in terms of the state of the key sites. 3. 3. A model of the mechanism by which key sites gain or lose activity is developed and the quantitative relations implied are derived. 4. 4. The experimental findings of the kinetic experiments are unified by assigning suitable values to the empirical parameters appearing in the equations describing the model.

Studies on activation of T4 bacteriophage by cofactor. III. Conditions affecting the activation process.

Abstract 1. 1. The effect of temperature on the rate of adsorption, on the degree of activity and on the rates of activation and of deactivation of cofactor-requiring T 4 bacteriophage is studied at different tryptophan by concentrations. 2. 2. The findings can be accounted for in terms of the model of the mechanism of activation of bacteriophage by cofactor proposed previously. 3. 3. The effects of pH and of ionic strength, the role of other cofactors and of inhibitors, and the characteristics of mutants T 4 of different cofactor requirement are discussed in terms of the model.

Studies on activation of T4 bacteriophage by cofactor: IV. Nascent activity☆

Abstract 1. 1. The phages released upon lysis of bacteria infected with a cofactor-requiring strain possess a nascent activity, which makes possible their adsorption in cofactor-free medium. 2. 2. Nascent activity is lost at a rate considerably below that of deactivation of tryptophanactivated T 4 (quiescent) bacteriophage. The rate of lss is very temperature-depenpendent. 3. 3. Individual nascent phages exist in various states of intermediate activity. 4. 4. Fresh nascent phages adsorb very much more slowly in liquid synthetic medium than in broth at 15° C but are adsorbed at nearly equal rates in both media at 37° C. 5. 5. Some of the activity imparted to nascent phages by addition of tryptophan is lost again at the slow rate characteristic of nascent activity. Degradation of nascent into quiescent phage appears to be due to loss of a cofactor as well as to a change in surface.