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 reaction