Molecular characterisation of autochtonous bacteria from spent engine oil contaminated soil in Dutse, Jigawa State, Nigeria: a foundational insight for plant-based biostimulant-enhanced bioremediation

Abstract

The indiscriminate discharge of spent engine oil (SEO) into the environment, especially in urban settlements poses a serious ecological and health concern due to the presence of toxic constituents such as heavy metals and aromatic hydrocarbons. Bioremediation that uses indigenous hydrocarbonoclastic bacteria offers a sustainable solution. This study was conducted to isolate and molecularly characterized SEO-degrading bacteria from contaminated soil in Dutse Mechanic Village, Jigawa State, Nigeria, as foundational input for future biostimulation research using native plant species. Soil samples were collected and cultured on Trypticase Soy Agar (TSA) enriched with SEO. Following morphological and biochemical characterization, selected isolates were subjected to molecular analysis using 16S rRNA gene sequencing. Gel electrophoresis revealed bands around 900 base pairs, and subsequent BLAST analysis confirmed the identity of the isolates as Pseudomonas aeruginosa and Bacillus cereus. Phylogenetic analysis using MEGA 11 software showed strong evolutionary relationships (≥98% similarity) with known hydrocarbonoclastic strains deposited in the NCBI database. The presence of these species both of which have been previously associated with hydrocarbon degradation underscores the bioremediation potential of native microbial communities in SEO-contaminated soils. This study serves as a foundation for future phytobiostimulation investigations employing indigenous plant stimulants such as Guiera senegalensis to enhance microbial degradation activity. The integration of molecular identification and phylogenetic profiling provides critical insights for developing site-specific bioremediation strategies.