Understanding the distribution, abundances and metabolic activities of microbial life in the subsurface is fundamental to our understanding of the role microbes play in many areas of inquiry such as terrestrial biogeochemical cycling and the search for extraterrestrial life. The deep terrestrial subsurface is known to harbor microbial life at depths of up to several kilometers where, in some cases, organisms live independently from the photosphere and atmosphere. Ancient fracture fluids trapped within the crystalline basement of the Canadian Precambrian Shield have been shown to be preserved on geologic timescales (millions to billions of years). Significant challenges exist when probing the deep terrestrial subsurface including the low biomass abundance, heterogeneous distribution of biomass, and the potential for matrix effects during sampling and analysis.
This Master’s thesis project has two main parts. The first study utilizes phospholipid fatty acid (PLFA) analysis to determine the extent of mineral matrices on the effectiveness of PLFA extraction and analysis from deep terrestrial subsurface samples. This was done by creating a bacterial dilution series of known concentration to inoculate one of two mineral matrices, granite or bentonite. This study revealed the presence of significant influence of mineral matrices on PLFA extraction and demonstrated the unreliability of PLFA-based biomass conversion factors with respect to complex microbial communities. The second study in this thesis combine PLFA analysis with stable carbon isotope analysis to characterize microbial communities associated with fracture fluids with mean residence times of ~1.4 Ga from boreholes located ~2.4km below the surface in Kidd Creek Mine, in Timmins, Ontario. Characterizing communities in subsurface systems has large implications for the search for life on other planets and moons, acting as an analogue environment. Large volumes of water from two boreholes, 12261 and 12299, were passively filtered for 6-12 months to collect microbial biomass. Borehole adjacent biofilms were also collected along with mine service water, which served as a control. All samples had significant biomass associated with them but were distinct in PLFA fingerprint and δ13C – PLFA signatures indicating the presence of three distinct microbial communities living in association with the fracture fluids and gases. These results have implications for the potential existence of ancient deep subsurface communities that have survived geologic time in isolation, in particular with relation to the subsurface of Mars, as well as give us insight into life on the early Earth. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23757 |
| Date | January 2018 |
| Creators | Ford, Sian Erin |
| Contributors | Slater, Gregory, Geography and Earth Sciences |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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