Browsing by Author "Brown, Damon Craig"

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    Calcium nitrate treatment of oil sand tailings for improved densification and reduced greenhouse gas emissions
    (2013-12-19) Brown, Damon Craig; Voordouw, Gerrit
    Canada contains one of the world’s largest bitumen reservoirs, the mining of which produces huge volumes of tailings stored in ponds where they persist as mature fine tailings (MFT) for decades, releasing up to 43,000 m3 d-1 biogenic methane from a single pond. MFT are typically treated with gypsum or polyacrylamide (PAM) to accelerate densification. Microbial reduction of sulfate and methane formation have been associated with improved densification through an unknown mechanism. Here, calcium nitrate treatment balanced with a carbon and energy source (molasses) was found to inhibit methanogenesis and reduced the number of syntrophs and methanogens present. Nitrous oxide emissions were found to be transient while the microbial cell counts increased suggesting biomass has a stronger influence on enhanced microbial densification than biogenic gas. Microbes associated with PAM treated tailings were found to remove amide groups and in the presence of oxygen create a nitrogen cycle while maintaining PAM flocs integrity.
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    Exploration of Multidrug Resistance Efflux Pumps (MDREPs) in Tolerance to Biocides
    (2022-06-14) Brown, Damon Craig; Turner, Raymond J; Gieg, Lisa; Chu, Angus; Hubert, Casey Russell James; Kumar, Ayush
    Biocides are broad-spectrum antiseptics used in industry and increasingly in domestic environments to control microbial growth. Microbial tolerance towards biocides is a well documented phenomenon in industries such as medical, water treatment and food processing but has not been well described in the oil and gas industry. A key form of acquired biocide tolerance is the acquisition of multidrug resistance efflux pumps (MDREPs) through horizontal gene transfer. In this project, I set out to determine if biocide tolerance could be determined and monitored using DNA-based quantitative PCR (qPCR) to facilitate the testing of samples from oil and gas pipelines where biocides are used to control microbiologically influenced corrosion. I first had to design primers for use in qPCR capable of detecting these poorly conserved genes using the annotated genomes of six species (Acetobacterium woodii, Bacillus subtilis, Desulfovibrio vulgaris, Geoalkalibacter subterraneus, Pseudomonas putida and Thauera aromatica) chosen to represent metabolic clades frequently identified in microbiologically influenced corrosion environments. During the creation of the model community, a surprising knowledge gap was identified correlating different microbial growth methods, so the decision was made to use optical density, ATP measurements, DNA concentrations and qPCR targeting 16S rRNA and determine how well these methods agreed. A mixed community of D. vulgaris, G. subterraneus, P. putida and T. aromatica was successfully grown reproducibly in bioreactors allowing for sessile and planktonic sampling following exposure to sublethal concentrations of biocides. Using the developed primers, the MDREP genes were quantified and ratioed to 16S rRNA copy numbers to track changes in the relative abundance. These results provide a proof-of-concept for the creation of a monitoring program aimed at targeting genetic markers and assessing microbial tolerance to biocides without costly sequencing.