Pyrene-degradation potentials of Pseudomonas species isolated from polluted tropical soils

Three Pseudomonas species isolated from oil polluted soils in Lagos, Nigeria were studied for their pyrene degradation potentials. These isolates exhibited broad substrate specificities for hydrocarbon substrates including polycyclic aromatic hydrocarbons, petroleum fractions and chlorobenzoates. All three isolates tolerated salt concentrations of more than 3%. They resisted ampicillin, cenfuroxime, but susceptible to ofloxacin and ciprofloxacin. Pseudomonas sp. strain LP1 exhibited growth rates and pyrene degradation rates of 0.018 h⁻¹ and 0.111 mg l⁻¹ h⁻¹ respectively, while P. aeruginosa strains LP5 and LP6 had corresponding values of 0.024, 0.082 and 0.017, 0.067 respectively. The overall respective percentage removal of pyrene obtained for strains LP1, LP5 and LP6 after a 30-day incubation period were 67.79, 66.61 and 47.09. Resting cell assay revealed that strain LP1 had the highest uptake rate. Strains LP1, LP5, and LP6 also used the ortho-cleavage pathway. Enzyme study confirmed activity of catechol 1,2-dioxygenase in all with values 0.6823, 0.9199, and 0.8344 μmol min⁻¹ mg⁻¹ respectively for LP1, LP3 and LP6. To the best of our knowledge, ours is the first report of pyrene-degraders from the sub-Saharan African environment.