Plasmid Profiling of Crude Petroleum Degrading Bacterial Strains Isolated from Polluted Soils in Ota, Nigeria

Abstract

Pollution from petroleum products is of public health concern because of its attendant health and environmental impacts. Aims: To study the biodegradation of Bonny light crude petroleum by bacteria isolated from soils of three different automobile mechanic workshops in Ota, Ogun State. Study Design: Contaminated soils from three (3) different auto-mechanic sources were enriched with Bonny light crude oil for a period of twenty-one (21) days after which the culture was changed and further enriched using crude oil as the only source of carbon and energy. Place and Duration of Study: Department of Biological Sciences (Microbiology Unit), Covenant University, Ota, Ogun State Nigeria, between June 2016 and March 2017. Methodology: Bacteria were isolated using standard microbiological techniques from enrichment of the soil samples in minimal salt medium (MSM) supplemented with 1% (v/v) crude petroleum as the only source of carbon and energy. The petroleum utilizing bacteria belonging to the genera Bacillus sp. (SB4), Pseudomonas sp. (SC8), Serratia sp. (SC11), and Acinetobacter sp. (SC12) were screened and subjected to oil degradation procedures. Gas Chromatographic (GC) analysis was used to analyze the component and percentage of the petroleum utilized. Plasmid curing and profiling were performed to determine whether the ability to utilize carbon is plasmid or chromosomally encoded. Results: Four (4) bacterial strains out of thirty-six (36) bacterial isolates were able to utilize petroleum as energy source. The GC fingerprints showed that both the aliphatic and aromatic components of crude petroleum were reduced to varying degree with the exception of nonadecane C19. Strain SC11 could not reduce anthracene, chrysene, benzo(a)pyrene and pyrene components of the crude petroleum. Strain SB4 depleted 24% - 57% of the aliphatic and 20% - 42% of the aromatics components while strain SC8 depleted 38% - 67% of the aliphatic and 30% - 79% of the aromatics components. However, strain SC11 only depleted 12% - 46% of the aliphatic and 13% - 29% of the aromatics components of the crude petroleum used. Conclusion: All organisms harbored plasmid which suggests that petroleum degradation capabilities could be plasmid encoded. This indicates that the petroleum utilizing bacteria which are part of the ecosystem could be used for natural remediation of petroleum polluted environments.