Plasmids of phenanthrene and dibenzothiophene-degrading bacteria isolated from produced water samples of oil production operations

Abstract

Some bacterial isolates from produced water that showed extensive degradation of Polycyclic aromatic hydrocarbons (PAH) in produced water were screened for the presence of catabolic plasmids targeted for the degradation of phenanthrene and dibenzothiophene (DBT) to determine whether the genes responsible for the degradation of these substrates reside in either plasmid or chromosomal DNA. When grown on phenanthrene, Acinetobacter lwoffi, Enterobacter sp. And Pseudomonas sp. harbored some plasmids with molecular weights less than 23.1kbp except Pseudomonas sp that harbored plasmids with molecular weight higher than 48.5 kbp. When Corynebacterium sp., Vibrio sp. and Pseudomonas aeruginosa were grown on dibenzothiophene (DBT), Plasmids with molecular weights higher than 48.5kbp were found in these organisms. Upon further investigation and curing with acridine orange, the resident plasmids were lost in phenanthrene and DBT degrading isolates but all the organisms retained their abilities to grow on these compounds. This result indicates that the genes for the degradation of phenanthrene and DBT in these organisms probably reside in the Chromosomal DNA as opposed to the Plasmid DNA.