Metagenomics insight into microbial dynamics in field-scale remediation of crude oil-polluted soil

Abstract

Background: The frequency of crude oil pollution has been on the increase following increased exploration, exploitation and production of energy from fossil fuel. Bioremediation has been shown to be eco-friendly and cost-effective method of oil spill remediation. In the Niger Delta, Landfarming has been the most used technique. The aim of this research was to employ metagenomic techniques to understand microbial dynamics during field-scale remediation in the Niger Delta in order to improve and reduce the time of remediation. Results: The surface (0.0 – 0.5m) sample had an extractable TPH value of 6231 mg/kg. The subsurface samples from 1m, 1.5m and 2.0m depths had extractable TPH concentration of 4836 mg/kg, 9112 mg/kg and 7273 mk/kg respectively. Proteobacteria dominated the soil microbial profile in all the samples studied as it made up at least 50% of each sample and mostly comprised of the class Alphaproteobacteria with variation only on day 18 and 36 which was mostly dominated by the class Gammaproteobacteria and Betaproteobacteria. Alpha diversity analysis revealed the presence of crude oil in the soil reduced microbial diversity. Principal coordinate analysis showed the microbial structure continually changed following changes in the chemical composition of the soil. Mycobacterium, Burkholderia, Rhodoplanes, Methylobacterium and Bacillus were the core OTUs detected during the period of remediation. Significant variation in pathway abundance particularly pathways for propanoate degradation, benzoate degradation, naphthalene degradation, fatty acid metabolism, polycyclic aromatic hydrocarbon degradation and degradation of xenobiotics were observed when the unpolluted soil was compared to the samples obtained during remediation. Conclusions: The findings from this study will greatly advance an already preferred landfarming oil spill recovery technique in the Niger Delta.