Characterisation of Crude Oil Polluted Soils and Bioremediation Potential of Indigenous Bacteria in Imo State

Crude oil spills remain a persistent environmental challenge in oil-producing communities across Nigeria, with significant consequences for soil fertility and ecosystem health. This study characterises the physicochemical properties of crude oil-polluted soils and evaluates the bioremediation potential of indigenous hydrocarbon-degrading bacteria isolated from contaminated sites in Imo State, South East Nigeria. Soil samples were collected from two spill-affected farms and one uncontaminated control site in Ohaji-Egbema Local Government Area. Physicochemical analysis assessed pH, organic carbon, total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, and total nitrogen. Bacteria were isolated using standard enrichment culture techniques on mineral salt medium supplemented with crude oil as the sole carbon source. Identified isolates were characterised morphologically and biochemically and subjected to in-vitro degradation experiments over a 42-day incubation period. Total petroleum hydrocarbon reduction was monitored gravimetrically at weekly intervals. Results show that Pseudomonas putida and Bacillus subtilis isolates achieved hydrocarbon degradation efficiencies exceeding 60 percent under optimised temperature and nutrient conditions. Soil pH and nitrogen content showed measurable improvement in bioremediated samples compared to untreated controls. The study demonstrates that autochthonous microorganisms hold practical promise for in-situ remediation of oil-contaminated agricultural lands in the Niger Delta region. Keywords: bioremediation, crude oil, Imo State, total petroleum hydrocarbons, indigenous bacteria