SEROLOGICAL PROPERTIES OF PHAGES OF AGROBACTERIUM RADIOBACTER

Neutralization tests using antisera for 4 of 16 Agrobacterium radiobacter phages indicated that all 16 phages belonged to one serological group. Within the group the phages were differentiated by the neutralization velocity constants, the K-values. Occasionally the antisera inactivated heterologous phages more rapidly than the homologous phages. With some systems the reactions were not of the first order throughout the course of neutralization. This anomaly in the kinetics was not due to hereditary antigenic inhomogeneity in the phage population, as indicated by curves obtained with the parent phage and with isolates which resisted neutralization. Adaptation of the phages to a heterologous host lowered the original K-values with homologous antisera without a change in the host range. None of the four antisera neutralized any of five phages of Agrobacterium tumefaciens, collectively lysing 16 strains of A. radiobacter, including homologous hosts of the phages used in the immunizations.