Benzene and Naphthalene Degrading Bacterial Communities in an Oil Sands Tailings Pond.

Fauziah F Rochman,Andriy Sheremet,Ivica Tamas,Joong-Jae Kim,Alireza Saidi-Mehrabad,Peter F Dunfield,Christoph W Sensen,Lisa M Gieg,Xiaoli Dong

doi:10.3389/fmicb.2017.01845

Abstract

Oil sands process-affected water (OSPW), produced by surface-mining of oil sands in Canada, is alkaline and contains high concentrations of salts, metals, naphthenic acids, and polycyclic aromatic compounds (PAHs). Residual hydrocarbon biodegradation occurs naturally, but little is known about the hydrocarbon-degrading microbial communities present in OSPW. In this study, aerobic oxidation of benzene and naphthalene in the surface layer of an oil sands tailings pond were measured. The potential oxidation rates were 4.3 μmol L−1 OSPW d−1 for benzene and 21.4 μmol L−1 OSPW d−1 for naphthalene. To identify benzene and naphthalene-degrading microbial communities, metagenomics was combined with stable isotope probing (SIP), high-throughput sequencing of 16S rRNA gene amplicons, and isolation of microbial strains. SIP using 13C-benzene and 13C-naphthalene detected strains of the genera Methyloversatilis and Zavarzinia as the main benzene degraders, while strains belonging to the family Chromatiaceae and the genus Thauera were the main naphthalene degraders. Metagenomic analysis revealed a diversity of genes encoding oxygenases active against aromatic compounds. Although these genes apparently belonged to many phylogenetically diverse taxa, only a few of these taxa were predominant in the SIP experiments. This suggested that many members of the community are adapted to consuming other aromatic compounds, or are active only under specific conditions. 16S rRNA gene sequence datasets have been submitted to the Sequence Read Archive (SRA) under accession number SRP109130. The Gold Study and Project submission ID number in Joint Genome Institute IMG/M for the metagenome is Gs0047444 and Gp0055765.

Highlights

The Athabasca oil sands reserves, located in northern Alberta, Canada, contribute more than 50% of the total crude oil production in Canada (National Energy Board, 2015)
The benzene and naphthalene oxidation rates measured were roughly linear over time (Supplementary Figures S2, S3)
The slightly higher than expected CO2 production indicates that less C is assimilated from these compounds than predicted by simple models, or that added benzene and naphthalene enhance the degradation of other hydrocarbon substrates available in oil sands process-affected water (OSPW) (Suthersan and McDonough, 1996)

Summary

Introduction

The Athabasca oil sands reserves, located in northern Alberta, Canada, contribute more than 50% of the total crude oil production in Canada (National Energy Board, 2015). For every cubic meter of bitumen extracted, 4 m3 of fluid tailings are produced. This consists of oil sands process-affected water (OSPW), sand, clays, residual bitumen and dissolved inorganic and organic compounds (Holowenko et al, 2002; Quagraine et al, 2005). OSPW is alkaline (pH 7.8–8) with high contents of salts (2.2 g L−1), metals, sulfides, naphthenic acids (NAs), and polycyclic aromatic compounds (PAHs) (Quagraine et al, 2005; Kelly et al, 2009, 2010; Saidi-Mehrabad et al, 2013). Little is known about activities in the more oxic surface water (Foght et al, 2017)

Methods

Results

Conclusion