MICROBIAL ABUNDANCE, DIVERSITY, AND POTENTIAL ACTIVITY IN BENTONITE CLAY
| dc.contributor.advisor | Stroes-Gascoyne, Simcha | |
| dc.contributor.advisor | Korber, Darren R | |
| dc.contributor.committeeMember | Vujanovic, Vladimir | |
| dc.contributor.committeeMember | Hynes, Russell K | |
| dc.contributor.committeeMember | Lawrence, John R | |
| dc.contributor.committeeMember | Farrell, Richard E | |
| dc.creator | Jalique, Daphne R 1988- | |
| dc.creator.orcid | 0000-0001-9409-4711 | |
| dc.date.accessioned | 2016-12-16T15:31:20Z | |
| dc.date.available | 2016-12-16T15:31:20Z | |
| dc.date.created | 2017-12 | |
| dc.date.issued | 2016-12-16 | |
| dc.date.submitted | December 2017 | |
| dc.date.updated | 2016-12-16T15:31:21Z | |
| dc.description.abstract | The Canadian deep geologic repository (DGR) concept for long-term safe storage and isolation of used nuclear fuel incorporates a multi-protective engineered barrier system. However, due to the inevitable presence of microorganisms and their metabolic products in a DGR, the integrity of the containers, and hence the repository, might be compromised. Therefore, the emphases of this thesis are to characterize and identify the microbial populations present in bulk and highly-compacted Wyoming MX-80 bentonite, to determine the conditions under which the survival and activity of microorganisms in highly-compacted bentonite clay (one of the engineered barriers) will be minimized or regulated, and to observe the microbial capacity to interact with bentonite particle under nutrient regime (clay-microbe aggregation study). To achieve these, culture-dependent and molecular biology methods (e.g., 16S rRNA sequencing), a range of analytical chemistry assays (e.g., sulfate turbidimetric method), pressure cell studies, microscopic technique (e.g., confocal laser microscopy (CLSM)), particle size analyses and laboratory-scale enrichment (or microcosm) assays were carried out. Culture-dependent techniques revealed the presence of spore-forming bacterial isolates belonging to phyla Actinobacteria and Firmicutes in bulk MX-80. Interestingly, when MX-80 bentonite was highly compacted, Gram-positive spore-formers were also identified after being exposed to the collective effect of > 2,000 kPa swelling pressure, 0.96 water activity, oxygen-free environment, and ≥ 1.6 g/cm3 dry density conditions for ~ 145 days and ~ 8 years. It was determined that microbial culturability was suppressed at or below background level (i.e., ≤ 2 x 102 Colony Forming Units per g) when the aforementioned parameters were applied and when 50 g/L NaCl solution infiltrated the highly-compacted bentonite (HCB). Sulfate reducing bacteria (SRB) in the HCB, however, were speculated to remain as spores during the incubation period since their microbial counts were similar at different dry densities. The enrichment assays for SRB containing bentonite clay slurry amended with carbon, electron donors and acceptors revealed that lactate was the preferred substrate for sulfidogenesis and that high salinity could impede the same process. Finally, the clay-microbe aggregation study showed that extracellular polymeric substance (EPS) contribute to the clay-microbe aggregation and that nutrient concentration, carbon substrate type and bentonite concentration affect EPS production. Overall, these studies are relevant to DGR operations because the results obtained will assist in understanding the potential consequences of microbial interactions with clay minerals. | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | http://hdl.handle.net/10388/7622 | |
| dc.subject | deep geologic repository bentonite | |
| dc.title | MICROBIAL ABUNDANCE, DIVERSITY, AND POTENTIAL ACTIVITY IN BENTONITE CLAY | |
| dc.type | Thesis | |
| dc.type.material | text | |
| thesis.degree.department | Food and Bioproduct Sciences | |
| thesis.degree.discipline | Applied Microbiology | |
| thesis.degree.grantor | University of Saskatchewan | |
| thesis.degree.level | Masters | |
| thesis.degree.name | Master of Science (M.Sc.) |