Abstract

Heavy metal contamination from motor mechanic workshop activities is a significant environmental and public health concern in urban Nigeria. This study isolated, screened and molecularly characterised heavy metal-tolerant bacteria from mechanic workshop soils in three area councils of the Federal Capital Territory (FCT), Abuja. Fifteen soil samples (five per location) were collected from Abuja Municipal Area Council – AMAC (Lugbe), Gwagwalada (Kuntunku) and Bwari (Dutse-Alhaji). Six bacterial species were identified by morphological and biochemical characterisation: Bacillus subtilis (37%), Pseudomonas aeruginosa (26%), Bacillus cereus (16%), Bacillus licheniformis (11%), Bacillus megaterium (5%) and Klebsiella pneumoniae (5%). Atomic Absorption Spectrophotometry (AAS) confirmed lead (Pb) concentrations of 86.11–86.31 µg/g and cadmium (Cd) of 9.63 µg/g, both exceeding WHO and FEPA permissible limits. In a standardised 5-day bioremediation assay with a commercial rhamnolipid biosurfactant as reference control, P. aeruginosa achieved the highest reductions: Pb by 11.09 ± 0.50 µg/g and Cd by 2.68 ± 0.09 µg/g (mean ± SD; n=3). Molecular characterisation of the most potent isolate (PA4) yielded a 789 bp 16S rRNA amplicon; BLAST analysis returned 100% identity to P. aeruginosa (GenBank HM224410; E-value 0.0). Neighbour-Joining phylogenetic analysis confirmed PA4 within the P. aeruginosa clade (bootstrap 100%). These results demonstrate the bioremediation potential of an indigenously isolated P. aeruginosa from FCT urban soils, while recognising that future studies should characterise the specific biosurfactant compounds and confirm activity through additional independent replicates.