The adsorption of bacteriophage phi-X174 to its host.

The adsorption of purified varphiX174 to E. coli C and to E. coli C cell walls was investigated. Adsorption was measured by assaying for unadsorbed plaque formers. The amount of irreversible and reversible adsorption depends upon pH and divalent ion concentration. Maximum irreversible adsorption occurs in 0.1 M CaCl(2) at 36 degrees C. There is no detectable reversible adsorption at conditions of pH and CaCl(2) concentration optimum for irreversible adsorption. Under these optimum conditions, diffusion is not the rate-limiting factor, and the encounter efficiency appears to be low. The rate constant is 1.0 x 10(-10) ml/sec. Phages adsorbed irreversibly to live cells cause infection and to the isolated cell walls apparently cause release of DNA. There is a specific varphiX174 receptor site on the mucocomplex portion of the cell wall.