Antigenic Differences Between Wild Type and Mutants of Bacteriophage λ

Summary The clear-plaque mutants, phage λgv (large plaque, virulent inducer mutant) and λgc (large clear plaque), both types isolated from the same wild-type phage λ, were neutralized by antiserum to phage λ+ at a much slower rate than λ+. For the anti-wild-type serum the neutralization constant (K) was 111 min.-1 for phage λ+, whereas for phage λgv it was only 27 min.-1. On the other hand, antiserum to phage λgv neutralized all three phages at similar rates (K = 84, 76 and 70 min.-1 for λgv, λgc and λ+ respectively). When anti-wild-type serum (K = 96 min.-1 for λ+) was tested against 50 independent λgv-type mutants, it gave a mean K value of 28 min.-1 with 42 of the isolates. Three of the isolates, with mean K value (93 min.-1) equivalent to that for λ+, produced plaques of unusual morphology in certain conditions. With the other five λgv isolates, the serum showed a mean K value of 53 min.-1. The same anti-wild-type serum neutralized phage λg (large turbid plaques) at approximately the same rate (K = 34 min.-1) as the majority of the λgv isolates, whereas for λmi (minute turbid plaque) the rate was greater (K = 123 min.-1) than for λ+ and was intermediate (K = 44 min.-1) for λm5co (medium cocarde plaque). These results indicate that the composition or structure of tail components can vary in different phage λ mutants, and this feature of the phage particle is not directly associated with loss of ability to lysogenize the host bacterium, Escherichia coli.