Interference effect of non-infectious particles in infection with phage f2

The titre of infectious phage particles in phage lysates stored at +4°C gradually fell. The inactivated particles retained their capacity for adsorption to male cell receptors, however, competing for the latter with infectious particles and thus protecting the cells from infection. The upper limit of the infected cell fraction in a F⁺ population fell abruptly with aging of the lysate even when the input of p.f.u. was kept constant. F₂ particles inactivated by u.v. radiation behaved similarly to particles inactivated spontaneously during storage of the lysate at +4°C.