Isolation and 16S rRNA-Based Identification of Hydrocarbon-Degrading Bacteria from Crude Oil-Impacted Soils in Ondo State

Hydrocarbon contamination from petroleum activities poses serious ecological risks in the oil-producing communities of Ondo State, located in Southwest Nigeria's onshore oil belt. Bioremediation using indigenous hydrocarbon-degrading bacteria offers a sustainable approach to soil restoration. This study isolated and identified hydrocarbon-degrading bacteria from crude oil-contaminated soils in Ilaje Local Government Area, Ondo State. Soil samples were collected from visibly contaminated and reference uncontaminated sites. Bacteria were isolated on Bushnell-Haas mineral salt medium supplemented with crude oil as the sole carbon source. Molecular identification was performed by PCR amplification and sequencing of the 16S rRNA gene using universal primers (27F/1492R). Phylogenetic trees were constructed using the neighbor-joining method in MEGA 11 software. Thirty-two bacterial isolates were obtained, predominantly belonging to the genera Bacillus, Pseudomonas, Rhodococcus, and Alcanivorax. Hydrocarbon degradation efficiency assays confirmed degradation rates ranging from 42% to 78% over 21 days under microcosm conditions. The diversity of competent degraders identified supports the feasibility of indigenous bioaugmentation strategies for oil-spill remediation in Ondo State coastal communities. Keywords: hydrocarbon degradation, 16S rRNA, bioremediation, crude oil, Ondo State.