Compositions of microbial communities associated with oil and water in a mesothermic oil field
Samples of produced water and oil obtained from the Enermark field (near Medicine Hat, Alberta, Canada) were separated into oil and aqueous phases first gravitationally and then through centrifugation at 20°C in an atmosphere of 90% N2 and 10% CO2. Biomass that remained associated with oil after gravitational separation (1×g) was dislodged by centrifugation at 25,000×g. DNA was isolated from the aqueous and oil-associated biomass fractions and subjected to polymerase chain reaction amplification with primers targeting bacterial and archaeal 16S rRNA genes. DNA pyrosequencing and bioinformatics tools were used to characterize the resulting 16S rRNA gene amplicons. The oil-associated microbial community was less diverse than that of the aqueous phase and had consistently higher representation of hydrogenotrophs (methanogens of the genera Methanolobus and Methanobacterium and acetogens of the genus Acetobacterium), indicating the oil phase to be a primary source of hydrogen. Many known hydrocarbon degraders were also found to be oil-attached, e.g. representatives of the gammaproteobacterial genus Thalassolituus, the actinobacterial genus Rhodococcus and the alphaproteobacterial genera Sphingomonas, Brevundimonas and Stappia. In contrast, all eight representatives of genera of the Deltaproteobacteria identified were found to be associated with the aqueous phase, likely because their preferred growth substrates are mostly water-soluble. Hence, oil attachment was seen for genera acting on substrates found primarily in the oil phase.
KeywordsMicrobial adhesion Oil biodegradation Synthrophy MEOR Methanogenesis DNA pyrosequencing
This work was supported by funding from Genome Canada, Genome Alberta, the Government of Alberta, Genome BC and a Natural Sciences and Engineering Research Council (NSERC) Industrial Research Chair Award to GV. The latter was also supported by Baker Hughes Canada, Commercial Microbiology Ltd., the Computer Modelling Group Ltd., ConocoPhillips Co., YPF, Saudi Aramco, Shell Canada Ltd., Suncor Energy Developments Inc. and Yara. We thank Ryan Ertmoed from Baker Hughes Canada for providing samples of produced oil–water mixtures, Dr. Sean Caffrey for organizational efforts and recommendations on the applications of statistical methods and Drs. Indranil Chatterjee and Rhonda Clark for their coordinating contributions.
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