Whole genome characterization and phenanthrene catabolic pathway of a biofilm forming marine bacterium Pseudomonas aeruginosa PFL-P1

Pseudomonas aeruginosa is a small rod shaped Gram-negative bacterium of Gammaproteobacteria class known for its metabolic versatility. P. aeruginosa PFL-P1 was isolated from Polycyclic Aromatic Hydrocarbons (PAHs) contaminated site of Paradip Port, Odisha Coast, India. The strain showed excellent biofilm formation and could retain its ability to form biofilm grown with different PAHs in monoculture as well as co-cultures. To explore mechanistic insights of PAHs metabolism, the whole genome of the strain was sequenced. Next generation sequencing unfolded a genome size of 6,333,060 bp encoding 5857 CDSs. Gene ontology distribution assigned to a total of 2862 genes, wherein 2235 genes were allocated to biological process, 1549 genes to cellular component and 2339 genes to molecular function. A total of 318 horizontally transferred genes were identified when the genome was compared with the reference genomes of P. aeruginosa PAO1 and P. aeruginosa DSM 50071. Further comparison of P. aeruginosa PFL-P1 genome with P. putida containing TOL plasmids revealed similarities in the meta cleavage pathway employed for degradation of aromatic compounds like xylene and toluene. Gene annotation and pathway analysis unveiled 145 genes involved in xenobiotic biodegradation and metabolism. The biofilm cultures of P. aeruginosa PFL-P1 could degrade ~74% phenanthrene within 120 h while degradation increased up to ~76% in co-culture condition. GC-MS analysis indicated presence of diverse metabolites indicating the involvement of multiple pathways for one of the PAHs (phenanthrene) degradation. The strain also possesses the genetic machinery to utilize diverse toxic aromatic compounds such as naphthalene, benzoate, aminobenzoate, fluorobenzoate, toluene, xylene, styrene, atrazine, caprolactam etc. Common catabolic gene clusters such as benABCD, xylXYZ and catAB were observed within the genome of P. aeruginosa PFL-P1 which play key roles in the degradation of various toxic aromatic compounds.