ORIGINAL PAPER Pyrene-degradation potentials of Pseudomonas species isolated from polluted tropical soils Oluwafemi S. Obayori Æ Matthew O. Ilori Æ Sunday A. Adebusoye Æ Ganiyu O. Oyetibo Æ Olukayode O. Amund Received: 29 February 2008 / Accepted: 2 June 2008 / Published online: 4 July 2008 Ó Springer Science+Business Media B.V. 2008 Abstract 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 ampi- cillin, 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 percent- age 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 lmol 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. Keywords Biodegradation Á Polycyclic aromatic hydrocarbons Á Pollution Á Pseudomonas Á Pyrene Introduction Petroleum is a major source of energy in the world today and Nigeria is one of the major oil producing countries (Amund et al. 1987). Polycyclic aromatic hydrocarbons (PAHs) are present as natural constituents of fossil fuels and are formed anthropogenically as a result of incomplete combustion of organic materials. They are, therefore, present in relatively high concentrations in refined products of fossil fuel and in every environment where fossil fuels and other organic materials are combusted. This, in com- bination with global transport phenomenon, results in their worldwide distribution (Kanaly and Harayama 2000). Pyrene is a pericondensed, four-ring polycyclic aromatic hydrocarbon (PAH). It is a regulated contaminant at sites polluted with petroleum (Kazunga and Aitken 2000). Interest in the biodegradation of PAHs such as pyrene is spurred in part by its mutagenicity and shared structure with carcinogenic PAH such as benzo(a)pyrene (Cerniglia 1992; Kanaly and Harayama 2000; Cheung and Kinkle 2001). Bacteria capable of degrading a wide range of hydrocarbons abound in the soil environment. Whereas microorganisms capable of utilising two- and three-ring PAHs as sole carbon and energy sources have been well- documented in the literature, until the late 1980s there was no literature on microorganisms capable of using four and five ring PAHs as sole carbon and energy sources (Heitk- amp et al. 1988). Pyrene is mainly degraded by actinomycetes such as Mycobacterium and Rhodococcus (Grosser et al. 1991; Walter et al. 1991; Kastner et al. O. S. Obayori (&) Faculty of Science, Department of Microbiology, Lagos State University, Ojo, Lagos, Nigeria e-mail: femiobayori@yahoo.com O. S. Obayori Á M. O. Ilori Á S. A. Adebusoye Á G. O. Oyetibo Á O. O. Amund Department of Botany and Microbiology, University of Lagos, Akoka, Lagos, Nigeria 123 World J Microbiol Biotechnol (2008) 24:2639–2646 DOI 10.1007/s11274-008-9790-7