Title: Klebsiella oxytoca; An efficient pyrene-degrading bacterial strain isolated from petroleum contaminated soil

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are the hazardous xenobiotic agents of oil production. One of the methods to eliminate hazardous compounds is bioremediation, which is the most efficient and cost-effective method to eliminate the harmful byproducts of crude petroleum processing. We isolated five pure bacterial isolates from petroleum-contaminated soil, four of which showed a robust growth on the PAH pyrene, as a sole carbon source. Various methods, viz, mass spectroscopy, biochemical assays, and 16S RNA sequencing ascertained the consistent identification of Klebsiella oxytoca. Scanning electron microscopy and Gram staining further demonstrated the characterization of the K. oxytoca. High-performance liquid chromatography of the culture supernatant of K. oxytoca grown in pyrene containing media showed that the cells started utilizing pyrene from the 6th day onwards and by the 12th day of growth 70% of the pyrene was completely degraded. A genome search for the genes predicted to be involved in pyrene degradation using Kyoto Encyclopedia of Genes and Genomes (KEGG) confirmed their presence in the genome of K. oxytoca. These results suggest that K. oxytoca would be a suitable candidate for removing soil aromatic hydrocarbons. In future, genes involved in pyrene mineralization and the pathways involved in its metabolism would be identified.