Methanotrophs in an Oil Sands End-Pit Lake and their Potential Co-oxidation of Naphthenic Acids
Date
2023-06
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Abstract
Methanotrophs possess the highly promiscuous enzyme, methane monooxygenase (MMO) which has been characterized to co-oxidize many substrates in conjunction with methane. As such, methanotrophs are hereby explored in the remediation of environmental pollutants such as naphthenic acids (NAs) in Base Mine Lake (BML), the first oil sands end-pit lake. BML is known to harbor an active methanotrophic population and can be explored for the co-oxidation or co-metabolism of compounds of concern in BML like NAs. We report on the dynamics of the methanotrophic population in the BML water column and sediment interface over time was explored using both 16S rRNA gene amplicon sequencing and pmoA gene (encoding particulate MMO) abundance by qPCR quantification. The results showed that methanotrophs can be up to 2.7 × 104 cells mL-1 of water by qPCR and are delineated by season, with Methylobacter dominating the water columns in winter and Methylococcus being the most abundant in the summer seasons based on 16S rRNA gene amplicon sequencing. Conversely, Methylococcus was most abundant in winter BML ice cover compared to Methylobacter spp. in this preliminary analysis of the methanotroph community associated with the ice cover in winter. In a mixed culture of methanotrophs enriched from BML water, we demonstrated that a surrogate NA, cyclohexane carboxylic acid (CHCA), could be biodegraded in a methane-dependent manner to non-detectable levels. Similarly, a tailings ponds methanotroph isolate, Methylicorpusculum oleharenae, was also able to degrade CHCA, strongly suggesting that MMO is implicated in the hydroxylation of NA. Overall, these findings may suggest that methanotrophs can play a role in the bioremediation and reclamation of organic compounds found in BML.
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Bioremediation
Citation
Nwosu, F. C. (2023). Methanotrophs in an oil sands end-pit lake and their potential co-oxidation of naphthenic acids (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.