NATIVE PLANT GROWTH PROMOTING RHIZOBACTERIA WITH REMARKABLE PHORATE METABOLISING ABILITIES AT CONCENTRATIONS MULTI-FOLD HIGHER THAN RESIDUAL CONCENTRATION PRESENT IN SOIL

Abstract

Native rhizobacteria were isolated from agriculture soil and evaluated for their pesticide remediation potential. Native rhizobacterial isolates (RBI1, RBI2, RBI3 and RBI4) employed in the study exhibited high levels of tolerance towards phorate (10% CG) registering  MIC (minimum inhibitory concentration) values, between 1450-2010 ppm. The isolates RBI1, RBI4 exhibited effeciency (35%-87%) to catabolise/co-metabolise phorate as sole energy (C\P) source at concentration as high as 500 ppm. FTIR analysis suggested evidence for degradtion of complex parent compound (phorate) to less complex degradtion metabolites. Disappearance of specific ester linkages in control (1025.43, 998.37 and 908.99cm^-1) suggested hydrolysis of ester bonds, which is a sure indication of  organophosphate‘s degrdation. Phorate degradation by native isolate was further quantified through HPLC analysis presenting 42% degradation (within 48hrs) at concentrations 10-15 fold higher (300 ppm) as compared to residual phorate reported in soils. Current study is the very first report providing a biologically safe option of rhizoremediation to degrade higher concentrations of persistent phorate residues, at concentrations rarely explored thus far. Thus the study provides substantial evidence regarding the potential of rhizobacterial isolates to be developed as bioinoculants and applied for accelerated remediation of toxic phorate residues.