Functional Gene Diversity of Selected Indigenous Hydrocarbon-Degrading Bacteria in Aged Crude Oil

Crude oil pollution has consistently deteriorated all environmental compartments through the cycle of activities of the oil and gas industries. However, there is a growing need to identify microbes with catabolic potentials to degrade these pollutants. This research was conducted to identify bacteria with functional degradative genes. A crude oil-polluted soil sample was obtained from an aged spill site at Imo River, Ebubu, Komkom community, Nigeria. Bacteria isolates were obtained and screened for hydrocarbon degradation potential by turbidometry assay. Plasmid and chromosomal DNA of the potential degraders were further screened for the presence of selected catabolic genes (C230, Alma, Alkb, nahAC, and PAHRHD(GP)) and identified by molecular typing. Sixteen (16) out of the fifty (50) isolates obtained showed biodegradation activity in a liquid broth medium at varying levels. Bacillus cereus showed highest potential for this assay with an optical density of 2.450 @ 600 nm wavelength. Diverse catabolic genes resident in plasmids and chromosomes of the isolates and, in some cases, both plasmid and chromosomes of the same organism were observed. The C230 gene was resident in >50% of the microbial population tested, while other genes occurred in lower proportions with the least observed in nahAC and PAHRHD. These organisms can serve as potential bioremediation agents

Distribution of PAH-ring hydroxylating dioxygenase genes in bacteria isolated from two illegal oil refining sites in the Niger Delta, Nigeria

Polyaromatic hydrocarbons (PAHs) are commonly found pollutants in the Niger Delta. They are comparatively persistent in the environment. Also, they distort healthy microbial interaction and pose high risk to human health owing to their toxic, mutagenic and carcinogenic properties. This research investigated the distribution of naphthalene dioxygenase gene (nahAc) and PAH-ring hydroxylating dioxygenase alpha genes (PAH-RHDα-GP) amongst bacteria isolated from two disparate locations (Bomu in Gokana LGA and Ngia Ama in Degema LGA, in Rivers State, Nigeria) used as illegal modular refining sites. Spread plate method was used to isolate PAH-degrading bacteria followed by identification, characterisation and phylogenetic analysis. Polymerase chain reaction was used to detect the nahAc and PAH-RHDα-GPgene sequences (from chromosomal DNA and plasmid) of the α-subunit of PAH-ring hydroxylating dioxygenase, using specific primer sets. Genera of Enterobacter, Shewanella, Burkholderia, Pseudomonas, Bacillus, Acinetobacter, Exiguobacterium and Stenotrophomonas were isolated from the two study sites. nahAc genes were found in the genomes of both Gram-negative and Gram-positive bacteria while PAH-RHDα-GPgenes were detected in all the plasmids recovered from Bomu-isolates. These findings inferred that the catabolic potential detected in the PAH-degrading bacterial community could be contributing to the in-situ biodegradation of PAHs. Keywords: α-subunit of PAH-RHD, Exiguobacterium, Artisanal refining, Polyaromatic hydrocarbons, Polymerase chain reactio

Microbial Consortium for Polycyclic Aromatic Hydrocarbons Degradation from Petroleum Hydrocarbon Polluted Soils in Rivers State, Nigeria

The study investigated the distribution of polycyclic aromatic hydrocarbon (PAH) degraders across two different petroleum hydrocarbon-polluted sites in the Niger Delta, Nigeria, and the ability of the reconstituted indigenous consortium to utilize these PAHs. Microorganisms were isolated after sample enrichment in naphthalene and anthracene, and biosurfactant production was measured using the emulsification index technique. PAH concentrations of approximately 6000 mg/kg and 9000 mg/kg in Tombia and Bodo were higher than the Department of Petroleum Resources (DPR) intervention limit of 40 mg/kg. The pH, soil texture and high conductivity affected microbial distribution significantly. A total of 12 bacteria from the genera Bacillus, Pseudomonas, Micrococcus and 3 fungal isolates (Fusarium, Aspergillus and Penicillium) from the 2 sites were able to utilize naphthalene and/or anthracene as sole carbon source. While the Tombia site had more microorganisms capable of PAH degradation with the redox indicator 2, 6-dichlorophenol indophenol (DCPIP) (10 bacterial and 3 fungal species), two bacterial species from Bodo were able to produce biosurfactant. The findings of this study indicate that indigenous microbes in the polluted sites are catabolically active and could be further stimulated for an effective eco-friendly and green removal of PAHs from oil-polluted soils while combined