Characterization of Multiple Polycyclic Aromatic Hydrocarbons (PAHs) Degrading Achromobacter xylosoxidans IITR150: Novel Insights from Whole Genome Analysis

Polycyclic aromatic hydrocarbons (PAHs) are biodegraded primarily by bacterial activities from polluted environments. From an oily sludge disposals site an Achromobacter xylosoxidans bacterium (designated as strain IITR150) was isolated with capability to grow and degrade multiple PAHs. Strain IITR150 was found to utilize naphthalene, phenanthrene, anthracene, benz(a)pyrene, benz(a)anthracene, and fluoranthene as the carbon source for its growth. Initially, the bacterium was screened based on its ability to turn indole into indigo and formed metabolites of the indole pathway such as indoxyl, isatin and indirubin. A 1014 bp gene encoding for a naphthalene 1,2-dioxygenase was found to initiate the biodegradation of naphthalene to have 42.85% homology to reported genes. Whole genome sequencing of A. xylosoxidans IITR150 had showed 5.9 Mb genome size containing 5625 predicted CDS. Among 5625 predicted CDS, cytochrome P450, catechol 2,3-dioxygenase (catE), naphthalene 1,2-dioxygenase system ferredoxin-NAD(P) ( +) reductase component (nahA), naphthalene 1,2-dioxygenase system, and ferredoxin components (nahB) genes were identified that indicated the metabolic potential of the bacterium for utilization of different aromatic compounds. Besides identification of PAHs degrading genes along with genomic insights suggests the robustness of the bacteria. Also, a cytochrome P450 (cytP450) enzymes that play a pivotal role in the detoxification of xenobiotics was found in IITR150, when aligned with three other cytP450 showed over 99.0% similarity at amino acid level. In conclusion, experimental and whole genome analysis provide capabilities of strain IITR150 involved in PAHs metabolism which could be useful in biodegradation of mixed PAHs contaminated soils.