Prevalence of polycyclic aromatic hydrocarbons (PAHs) degrading bacteria in contaminated tropical soil in Lagos, Nigeria: involvement of plasmid in degradation

Recalcitrant pollutants such as polycyclic aromatic hydrocarbons (PAHs) are difficult to degrade and have been the focus for biodegradation. They form a class of pollutant on a global scale. In an attempt to contribute to the search for suitable microbial culture with potential to biodegrade low and high molecular weight PAHs, bacterial strains were isolated from engine-oil polluted sites in Lagos, Nigeria. These isolates were evaluated for possession of plasmid DNA and the role it played in PAH degradation. Out of sixteen strains isolated, two were Gram negative while the others were Gram positive isolates. They belonged to genera Micrococcus, Staphylococcus, Kurthia sp., Acinetobacter, Pseudomonas and Corynebacterium. All the isolates grew on the PAHs (anthracene, fluoranthene and pyrene) at varying rates utilizing them as sole sourceof carbon and energy. All the isolates also possessed plasmid DNA ranging from 17.8 to 38.9 kbp. Subjection of plasmid cured isolates to PAHs biodegradation suggest that PAHs degradation may be plasmid and/orchromosomally mediated depending on the bacterial isolate and PAHs being degraded. This study has revealed that different compounds induce varied genetic changes in bacterial isolates in response to the stimuli