Aerobic Hydrocarbon-degrading Microbial Communities in Oilsands Tailings Ponds

Oilsands process-affected water (OSPW), produced by the surface-mining oilsands industry in Alberta, Canada, is alkaline and contains salts, various metals, and hydrocarbon compounds. In this thesis, aerobic communities involved in several key biogeochemical processes in OSPW were studied. Degradation of several key hydrocarbons was analyzed in depth. Benzene and naphthalene were used as models for aromatic hydrocarbons, in which their oxidation rates, degrading communities, and degradation pathways in OSPW were researched. The potential oxidation rates were 36.7 μmol L-1 day-1 for benzene and 85.4 μmol L-1 day-1 for naphthalene. Via stable isotope probing (SIP), and high-throughput sequencing of 16S rRNA gene amplicons, it was discovered that strains of the genera Methyloversatilis and Zavarzinia were the main benzene degraders, while Thiococcus and Pseudomonas were the main naphthalene degraders. Cultivated strains of Zavarzinia and Pseudomonas were shown to be growing on benzene and naphthalene. Metagenomics analysis revealed genes encoding oxygenases active against aromatic compounds, as well as catechol oxidases. Although these belonged to many phylogenetically diverse bacteria, only few bacteria were predominant in the SIP experiments. A highly divergent pmoA-like gene was also detected in the metagenome data. Here, the possibility of this gene allowing growth on short alkanes (C1 to C3) was examined. This gene was investigated via SIP and quantitative PCR. Results showed that the monooxygenase encoded by the gene has high affinity toward ethane and mostly propane. For the study of lighter hydrocarbons, methane, ethane, and propane were chosen as model compounds. OSPW was capable of supporting methane oxidation with a rate of 108.2 μmol of CH4 L−1 OSPW d−1, ethane oxidation with a rate of 83.2 μmol of C2H6 L−1 OSPW d−1, and propane oxidation with a rate of 58.6 μmol of C3H8 L−1 OSPW d−1. SIP analysis uncovered Methyloparacoccus to be predominant in methane-incubated samples, whereas Methyloversatilis was predominant in ethane and propane-incubated samples. SIP technique was also employed to study photosynthetic bacterial communities and indigenous aerobic bacterial communities that assimilate methanol, acetate, and protein extracts. All OSPW photosynthetic ‘heavy-DNA’ samples were dominated by unidentified Planctomycetes. Predominant groups in methanol, acetate, and protein extract-SIPs were Betaproteobacteria, Alphaproteobacteria, and Bacteroidetes. Finally, via a modified cultivation technique, a novel Verrucomicrobia was isolated from OSPW. The aerobic bacterium was named Oleiharenicola alkalitolerans gen. nov., sp. nov., and it was studied in depth via phylogenetic, chemotaxonomic and whole-genome sequencing techniques.

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