HEAVY METAL TOLERANCE AND HYDROCARBON-DEGRADING POTENTIAL OF INDIGENOUS SOIL BACTERIA ISOLATED FROM OIL SPILL SITES IN BERE COMMUNITY RIVERS STATE, NIGERIA

Contamination from oil spills in Nigeria's Niger Delta has led to widespread co-contamination of soils with petroleum hydrocarbons and heavy metals, creating significant environmental and ecological problems. This research aimed to test the hydrocarbon-degrading capacity and heavy metal tolerance of indigenous soil heterotrophic bacteria isolated from oil-polluted sites in the Bere community in the Gokana Local Government Area of Rivers State, and to assess their potential for bioremediation. The results of the physical and chemical analysis of the soils showed a pH range between 6.51 and 6.79 in the polluted soils as compared to 5.60 in the control soil; the organic carbon range was 2.9–3.18% in the polluted soils and 2.50% in the control soil. The mean concentration of copper and Iron in the polluted soil was 199.5 and 143.6 mg/kg, respectively. The total heterotrophic bacterial (THB) counts ranged from 2.8 × 10⁵ to 3.4 × 10⁵ CFU/g, and the hydrocarbon-utilizing bacterial (HUB) counts ranged from 6.7 × 10⁵ to 8.8 × 10⁵ CFU/g. Potential for degradation of hydrocarbons was determined by the 2,6- dichlorophenolindophenol (DCPIP) reduction assay in Bushnell–Haas broth containing 1% crude oil after 144 hours. Among the sixteen isolates characterized, Salmonella spp (DJ15) and Proteus spp (DJ16) showed exceptional capability for hydrocarbon degradation. Heavy metal tolerance assays with Fe³⁺ and Cu²⁺ revealed different resistance profiles, with isolates JD14 and JD16 being very high copper-tolerant. The results suggest that indigenous bacteria from oil-polluted soils may possess hydrocarbon-degrading and heavy-metal tolerance traits that may be useful for future bioremediation applications.