Table 1_Hydrocarbon degradation and genomic insights of Klebsiella pneumoniae from oil-contaminated soils in Guimaras Island, Philippines.docx

Klebsiella was previously found to be the dominant genus of a hydrocarbon-degrading, diesel-enriched microbial consortium from oil-spill contaminated soils in Guimaras Island, Philippines. However, the species-level identity, individual degradation efficiency, and genomic determinants of metabolic pathways and environmental stress adaptation remain unknown, limiting the understanding of the ecological role and bioremediation potential of Klebsiella species. This study isolated, characterized, and evaluated the hydrocarbon degradation efficiencies of Klebsiella species from the consortium. From 110 putative Klebsiella colonies, 11 isolates showed significantly different degradation capacities of at least 66% on diesel, hexane, hexadecane, and xylene, suggesting diversity at the species and strain level, and substrate preference. Isolate KLMG-HD-125 demonstrated complete oxidative degradation of short- and mid-chain n-alkanes (C11–C25) in diesel, indicating a broad substrate range and strong petroleum degradation potential. Whole genome sequence analysis confirmed the identity of KLMG-HD-125 as Klebsiella pneumoniae with a genome size of 5.55 Mb and GC content of 57.2%. It harbors genes responsible for alkane and xylene degradation, and pathways to respond to oxidative, membrane, and solvent stress, indicating ecological fitness, allowing the isolate to remain metabolically active in potentially toxic petroleum-impacted environments. Specifically, the presence of ladA (LadA-like FMN-dependent monooxygenase), adhP (primary alcohol dehydrogenase), and adh (long-chain aldehyde dehydrogenase) indicates the pathway for terminal oxidation of alkanes. Although 11 virulence-associated genes were identified in KLMG-HD-125, the hypervirulence determinants were absent. Together with its environmental origin, these findings indicate that KLMG-HD-125 is potentially opportunistic rather than an obligate pathogen. Overall, KLMG-HD-125 is equipped with phenotypic and genomic traits essential for hydrocarbon remediation, specifically of n-alkanes, and ecological fitness to persist in petroleum-impacted environments, though its potential pathogenicity requires careful biosafety assessment prior to environmental application.