Phage adsorption forces: T-even coliphage binding to Escherichia coli most likely depends on which predominant type of interaction at the initial adsorption step?

Introduction / Context:
The first step in bacteriophage infection is adsorption to the bacterial surface via tail fibers or spikes. Understanding the physicochemical nature of this contact clarifies why environmental conditions (pH, ionic strength) strongly affect phage attachment and host range.

Given Data / Assumptions:

• T-even phages (e.g., T2, T4) target specific outer membrane receptors on E. coli.
• Initial binding is reversible and sensitive to ionic conditions.
• Only one option should reflect the primary initiating force.

Concept / Approach:
Initial phage–cell encounters are dominated by long-range, noncovalent forces (notably electrostatic attraction between charged surfaces). This reversible stage is followed by tighter, short-range contacts and conformational changes that lead to irreversible adsorption. Covalent bonding does not mediate routine adsorption; hydrophobic contacts may contribute secondarily but are not typically the initiating, dominant force for T-even phages.

Step-by-Step Solution:
Identify reversible adsorption as the first step. Recall dependence on ionic strength and pH, implicating electrostatics. Exclude covalent bonding as incompatible with rapid, reversible binding. Select electrostatic interaction as the best primary descriptor.

Verification / Alternative check:
Experimental modulation of divalent cations and salt concentrations profoundly alters T4 adsorption efficiency, consistent with charge-governed interactions at initial contact.

Why Other Options Are Wrong:
Hydrophobic forces may contribute later but are not the dominant, controllable variable in early reversible binding; covalent bonds and disulfide formation are not involved in normal adsorption events; “All of these” is incorrect because covalent bonding is not used.

Common Pitfalls:
Assuming any strong interaction must be covalent; biological adhesion commonly exploits multiple weak, reversible noncovalent forces coordinated in space.

Final Answer:
Electrostatic interaction.