Restoration of crude oil-contaminated soil using microbes with degradative and plant-growth-promoting abilities

Microorganisms with traits such as biosurfactant production, hydrocarbonoclastic ability, and PGP activity can be used to restore the soil health of agricultural fields affected by oil pollution. In this study, the ability of a microbial consortium of four microbial strains was assessed to degrade petroleum hydrocarbons and restore the health of oil-contaminated soil. The candidates for bioremediation were selected based on various screening assays (Haemolytic assay, protease activity, siderophore production, ammonia production, and DCPIP assay). The selected candidates for the consortium were: OC4 (Bacillus paralicheniformis KJ-16*), OC9 (Ochrobactrum intermedium NBRC 15820*), Pseudomonas aeruginosa NCIM 5514, and Pseudomonas aeruginosa MTCC 7815. Further, a soil microcosm study was done over 90 days with a focus on plant parameters such as chlorophyll content and concentration of H₂O₂ and MDA in leaf tissue. Finally, the residual hydrocarbons in the soil were assessed by GC-MS and FTIR analysis. The results indicate a reduction in the total chlorophyll content and the accumulation of H₂O₂ and MDA. These results are indicative of oxidative stress in plants. The FT-IR and GC-MS data positively dictate the success of bioremediation via microbial consortium. The consortium of four microbial strains developed in this study have the potential to bioremediate oil-contaminated soil.