Immunological Changes in Azir-Mutants of Bradyrhizobium sp. (Cajanus)

Antigenic constitution of an efficient nitrogen fixing strain of Bradyrhizobium sp. (Cajanus) ARS39 was compared with its six azide resistant mutants. The wild type strain contained minimum six antigens. Five of them were bound antigens and reacted only when they were released by sonication of cells followed by heat treatment. Azide resistance caused changes at minimum of three antigenic sites in the mutants. This led to the deletion of two most slow diffusing antigens and further resolution of a strain specific, moderately diffusing antigen. No change was observed in fast diffusing antigens which are considered species/group-specific. All the six mutants showed identical antigenic constitution though they were selected independently.