ISOLATION AND CHARACTERIZATION OF RHIZOBIUM FROM LEGUMES AND ITS ASSOCIATION WITH PLASMIDS

Abstract

In an attempt to check the direct involvement of plasmid in nodulation and nitrogen fixation, rhizobia were isolated from two legumes; Arachis hypogea (groundnut), Phaseolus vulgaris (beans) and from the soil as control. They were purified and subjected to various morphological, cultural, biochemical analysis and antibiotics test. All the strains showed resistance to most of the antibiotics but exhibited high resistance against Ciprofloxacin and Ofloxacin. The isolates were then subjected to plasmid DNA isolation and their molecular sizes were determined in gel electrophoresis using standard molecular marker. In addition, plates of rhizobial strains treated with UV radiation and plate without UV treatment were independently used to inoculate a sterilized soil where the beans and groundnut were planted followed by appropriate controls. The results showed that rhizobium natural environment is very necessary for proper nodulation and also that plasmid has a role to play in the process of nodulation