INCIDENCE OF GRAM-NEGATIVE BACTERIA ISOLATED FROM OIL POLLUTED WORKSHOPS IN IRELE LOCAL GOVERNMENT AREA OF ONDO STATE

Mechanic workshops, while essential to transportation and commerce, are silent contributors to environmental degradation, releasing used engine oil, lubricants, and metallic debris into surrounding soils. These pollutants introduce hydrocarbons, heavy metals, and other toxic compounds that reshape soil chemistry and disrupt native microbial ecosystems. This study explored the bacterial microflora inhabiting oil-polluted soils from selected mechanic workshops in Irele Local Government Area, Ondo State, Nigeria. Soil samples, collected from visibly contaminated sites at a depth of 0–15 cm, underwent microbiological isolation, morphological observation, and biochemical characterisation following standard protocols, with identification based on Bergey’s Manual of Systematic Bacteriology. Physicochemical properties including pH, temperature, and electrical conductivity were also assessed. Two species emerged as dominant: Klebsiella spp. (Gram-negative short rods, catalase-positive, oxidase-negative, non-motile) and Morganella morganii (Gram-negative cocci, catalase-positive, oxidase-negative, coagulase-positive, non-motile). Soil pH ranged from 4.86 to 5.77, reflecting acidity commonly generated during hydrocarbon breakdown, while electrical conductivity (50.3–109.3 μS/cm) indicated elevated ionic content, possibly from metal leachates. These isolates demonstrated physiological adaptations incuding oxidative stress tolerance and selective carbohydrate metabolism that enable persistence under combined hydrocarbon and heavy-metal stress. The detection of Klebsiella spp. and M. morganii in this context broadens current knowledge of hydrocarbon-adapted bacterial communities in Nigeria, highlighting their potential role in natural attenuation processes. This work not only provides baseline data for future bioremediation research but also underscores the urgent need for sustainable waste-handling practices in local mechanic workshops to safeguard soil health.