Cultural, Physiological and Serological Analysis of Azir Mutants of Bradyrhizobium sp (Cajanus)

Abstract

Mutants of Bradyrhizobium sp (Cajanus) ARS39, resistant to different concentrations of sodium azide (110 to 200 μg ml−1) were isolated and characterized for the cultural, physiological and serological properties; and were compared with the wild type strain ARS39. Among the 51 Azir mutants, only one was found to be a non-nodulating and acid producer. A large number of Azir mutants showed variations in more than one property viz. antigenic constitution and tolerance to temperature and pH. The variations in these properties were not always related to their level of azide resistance, indicating that mutation to sodium azide could involve more than one gene locus. Antigenic analysis could further resolve differences among the mutants, many of which were otherwise identical in all other characteristics. Some of the mutants belonging to same serogroup also differed significantly in their resistance to sodium azide, indicating that resistance to different concentrations of sodium azide may not always induce identical antigenic changes. Three mutants Azi29, 36 and 35, showing striated growth, were the only mutants to exhibit altered protein profile also. This suggests that there is a possibility of link between the altered growth morphology and the protein profile of mutants.