Benzo[a]pyrene degrading Bacillus altitudinis AR19 isolated from Digboi oil refinery soil (India)

Benzo[a]pyrene (B[a]P) is a five-ring polycyclic aromatic hydrocarbon (PAH) recognized as a potent carcinogen and persistent environmental pollutant, highly resistant to microbial degradation. In this study, a B[a]P-degrading and biosurfactant producing bacterium, Bacillus altitudinis AR19, was isolated from the Digboi oil refinery site in Assam, India. The isolate was screened using the spray plate technique, and its morphological features and cell viability were examined by scanning electron microscopy (SEM) and flow cytometry. Biosurfactant production was confirmed through drop collapse, oil spreading, and emulsification assays. Taxonomic identity was established using average nucleotide identity (ANI), and comparative pangenome analysis was performed among B. altitudinis (Taxonomy ID: 1178544), Bacillus pumilus (Taxonomy ID: 1408), Mycolicibacterium vanbaalenii (Taxonomy ID: 110539), and B. altitudinis AR19. The results highlight that several mechanisms including osmolyte accumulation, biosurfactant production, and mechanosensitive ion channels play key roles in enabling B. altitudinis AR19 to tolerate and degrade B[a]P. This study demonstrates the potential of B. altitudinis AR19 as a promising candidate for bioremediation of PAH-contaminated environments.