Crude oil/petroleum hydrocarbons (PHs) are major pollutants worldwide. In the present study, three bacterial isolates -Pseudomonas aeruginosa BB-BE3, P. aeruginosa BBBJ, and Gordonia amicalis BB-DAC were selected for their efficient hydrocarbon degradation and plant growth promotion (PGP) abilities. All three isolates were positive for siderophore production, phosphate solubilization, and IAA production, even in the presence of crude oil. The rhizoremediation ability was validated through pot trials where all three isolates promoted the growth of the Azadirachta indica plant in crude oil-contaminated soils. Treatment with the combination of the plant (A. indica) and bacteria, i.e., Pseudomonas aeruginosa BB-BE3; P. aeruginosa BBBJ; Gordonia amicalis BB-DAC showed 95.71, 93.28, and 89.88% removal of TPHs respectively, while the treatment with the plant (only) resulted in 13.44% removal of TPHs whereas, in the control (Sterile bulk soil + Crude oil), the hydrocarbon removal percentage was only 5.87%. The plant tissues were analyzed for catalase (CAT) and peroxidase (POX) activities, and the plants augmented with bacterial strains had significantly low CAT and POX activities as compared to uninoculated control. Therefore, the results suggest that the A. indica plant, in symbiotic association with these hydrocarbonoclastic rhizobacteria, could be used for bioremediation of crude oil-polluted soil.
Keywords: Azadirachta indica; Petroleum hydrocarbons; enzyme activity; hydrocarbonoclastic PGPR; rhizoremediation; stress responses.
The main objective of the present study is to evaluate the potential of plant–microbe associations, also including Gordonia amicalis with the Azadirachta indica, for the rhizoremediation of petroleum hydrocarbon (PHs) polluted soil. For rhizoremediation strategy, a stable plant-bacteria partnership is important, along with effective remediation, and the Gordonia amicalis–Azadirachta indica pair is being described here for the first time, for this purpose. This plant-microbe pair was highly effective as also validated through pot trials. The hydrocarbonoclastic rhizobacteria (G. amicalis BB-DAC), in symbiotic association with the A. indica plant, has significantly degraded TPHs.