Background: Petroleum polycyclic aromatic hydrocarbons (PAHs) are known to be toxic
and carcinogenic for humans and their contamination of soils and water is of great environmental concern.
Identification of the key microorganisms that play a role in pollutant degradation processes is
relevant to the development of optimal in situ bioremediation strategies.
Objective: Detection of the ability of Pseudomonas fluorescens AH-40 to consume phenanthrene as a
sole carbon source and determining the variation in the concentration of both nahAC and C23O catabolic
genes during 15 days of the incubation period.
Methods: In the current study, a bacterial strain AH-40 was isolated from crude oil polluted soil by
enrichment technique in mineral basal salts (MBS) medium supplemented with phenanthrene (PAH)
as a sole carbon and energy source. The isolated strain was genetically identified based on 16S rDNA
sequence analysis. The degradation of PAHs by this strain was confirmed by HPLC analysis. The detection
and quantification of naphthalene dioxygenase (nahAc) and catechol 2,3-dioxygenase (C23O)
genes, which play a critical role during the mineralization of PAHs in the liquid bacterial culture were
achieved by quantitative PCR.
Results: Strain AH-40 was identified as pseudomonas fluorescens. It degraded 97% of 150 mg phenanthrene
L-1 within 15 days, which is faster than previously reported pure cultures. The copy numbers
of chromosomal encoding catabolic genes nahAc and C23O increased during the process of phenanthrene
Conclusion: nahAc and C23O genes are the main marker genes for phenanthrene degradation by
strain AH-40. P. fluorescence AH-40 could be recommended for bioremediation of phenanthrene contaminated