Investigating indigenous bacteria for efficient biodegradation of diesel hydrocarbons in contaminated soils

Petroleum hydrocarbon contamination poses significant environmental and health risks, necessitating sustainable bioremediation approaches. This study isolated and characterized diesel-degrading bacterial strains from petroleum-contaminated soils in Peshawar, Pakistan. Two strains, identified as <i>Acinetobacter baumannii</i> (Aii) and <i>Acinetobacter calcoaceticus</i> (Bi) through 16S rRNA sequencing and biochemical assays, were evaluated for their bioremediation potential. Enrichment cultures on Bushnell-Haas medium with diesel as the sole carbon source demonstrated vigorous growth for both strains. Gas chromatography-mass spectrometry (GC-MS) analysis confirmed their ability to degrade aliphatic and aromatic hydrocarbons. <i>Acinetobacter baumannii</i> exhibited preferential degradation of high-molecular-weight alkanes (C₂₁–C₂₈; up to 78.35%), while strain Bi efficiently metabolized short- to mid-chain alkanes (C₈–C₂₀; up to 87.01%) and aromatics (up to 74.36%). Overall, Aii and Bi degraded 62.20% and 62.33% of total diesel hydrocarbons, respectively. Identified metabolic intermediates suggested enzymatic pathways involving monooxygenases and dioxygenases. The complementary substrate specificities of these strains highlight their potential for synergistic application in diesel-contaminated site remediation. This study underscores the significance of indigenous microbial resources in developing cost-effective, sustainable solutions for petroleum pollution mitigation, with potential for field-scale bioremediation applications.