Lysis inhibition with a mutant of bacteriophage T5

Abstract

Lysis inhibition has been demonstrated with a small-plaque mutant of T5, designated M12. This appears to be the first example of the phenomenon outside the T-even system. M12 and T5 appear identical in host range, adsorption rate, serum neutralization, and injection rate, but differ in minimal latent period in single infection (45–50 minutes for M12 as against 37 minutes for T5) and in plating efficiency under various conditions. Evidence of lysis inhibition in multiply infected cultures was obtained with M12, but not T5, by observations on the clearing of turbid cultures, one-step growth experiments, and microscopic examination. The best demonstrations in one-step growth experiments were obtained when young bacterial cultures ( Escherichia coli strain F, smooth derivative of FCb) were multiply infected with M12 in a single input (multiplicity of 6–8 adequate) and further incubated undiluted for 30–40 minutes, or diluted earlier into sonicated extracts of B 5 . The latter do not affect the lysis of cultures singly or multiply infected with T5 or singly infected with M12. One-step growth experiments suggest multistep release of phage in lysisinhibited cultures. A possible explanation, actual multiplication of the infected bacteria, received no support from microscopic studies.