Molecular Characterization of Hydrocarbon-Degrading Bacteria in Oil-Contaminated Soils from Mechanic Workshops in Abakaliki Metropolis, Southeastern Nigeria

Engine oil is a hazardous pollutant that contaminates soil, water, and ecosystems. This study isolated and characterized hydrocarbon-degrading bacteria from engine oil-contaminated soils in three (3) mechanic workshops in Abakaliki, Ebonyi State, Nigeria. The bacterial populations were enumerated, and their degradation capacity was assessed using 2,6-dichlorophenol indophenol (DCPIP). Sample S2b had the lowest bacterial count (2.04 × 105 CFU/g; 0.89% of total isolates), while sample S2a had the largest bacterial population (1.01 × 107 CFU/g; 44% of total isolates). The bacterial counts obtained from the soil samples reflect the abundance of hydrocarbon-degrading microorganisms naturally present in the oil-contaminated environment. The isolates, including Pseudomonas putida, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Proteus mirabilis, demonstrated hydrocarbon degradation potential and were identified based on their Gram reactions and molecular characteristics using 16S rRNA. The results suggest that these native bacterial isolates can be used for bioremediation of oil-contaminated environments, providing a promising approach for pollution control and soil restoration in the region.