Biological responses of symbiotic Rhizobium radiobacter strain VBCK1062 to the arsenic contaminated rhizosphere soils of mung bean

The rationale could be that mung bean is cultivated in areas of arsenic contamination and therefore it is worth investigating how Rhizobium is impacted by arsenic exposure. The objective(s) of the study deals with relationship between Rhizobium metal tolerance and its adaptations to metal stressed environment. The selected strain was recovered from root nodules of Vigna radiata, based on viscous EPS production and arsenic tolerant capacity, identified as R. radiobacter by 16S rDNA sequencing. Batch studies were performed to evaluate toxic effects of heavy metal ions in decreasing order of MIC As(V) (10mM), Cu(1.5mM), Pb(0.18mM), Cr(0.1mM), Ni(0.08mM) and Cd(0.04mM). Scanning electron microscopy analysis of Arsenic resistant strain revealed evident changes in cell morphology. SDS-PAGE results showed altered expression of proteins in response to arsenate. One unique protein of approximately 21kDa was highly expressed in 5mM arsenate, but same protein was down regulated in 10mM arsenate. The exopolysaccharide components such as total carbohydrates, proteins and uronic acids were significantly enhanced by 41%, 25% and 33% (P Value