Antiserum Inactivation of Electrophoretically Purified M13 Diploid Virions: Model for the F-Specific Filamentous Bacteriophages

Antiserum inactivation experiments were carried out on electrophoretically purified diploid virions from a cross between two complementing amber mutants of phage M13. The total (homozygous plus heterozygous) diploid population, assayed on a permissive host where only one genome is needed for plaque formation, was inactivated at the same rate as haploids. Heterozygous diploids, assayed on a nonpermissive host, where both genomes are needed for plaque formation, were twice as sensitive as haploids and the total diploid population. These results have led us to propose a model for serum inactivation of the F-specific filamentous phages. According to this model, phage-neutralizing antibodies attach anywhere along the length of the phage and allow the phage to penetrate only up to the first bound antibody molecule.