Understanding the distribution, abundances, and metabolic activity of microbial life in terrestrial environments is fundamental to our understanding of the role that microbial life can play in many areas of interest, such as biogeochemical cycling and microbially assisted degradation, and as the foundational knowledge for the search for extraterrestrial life. Depending on location, sufficient biomass or extraction procedure can pose significant challenges to quantify and identify the microbes present in a system due to low biomass, cell resistances, or matrix effects.
This Master’s Thesis project has two main aspects. The first study utilizes phospholipid fatty acids (PLFA) analysis to determine the influence of methane and other petroleum hydrocarbons on the Base Mine Lake (BML) Pit Lake (PL). This was done by extracting biofilm units that were deployed into BML at different seasons and depths. PLFA biomarkers were utilized to determine cell abundance on biofilms as well as microbial community composition. This study revealed abundant microbial growth on biofilm units. The observed microbial composition on the biofilm units was comparable to that of the water column, with notable increase of C16:1 and polyunsaturated PLFA in both the epilimnion and hypolimnion, which contains biomarkers consistent with methanotrophy (C16:1) and phototrophy (polyunsaturates). Radiocarbon analysis of PLFA from biofilm units demonstrated that the carbon source used by the microbial communities within the system was derived from petroleum carbon, with petroleum carbon contributing up to 90% of the carbon in the PLFA. Strong stable isotopic depletion of biomarker lipids (δ13C = -51 ‰) for methanotrophy indicated the use of methane derived carbon by the community. In the epilimnion methanotrophy was indicated to be less important and indications of photosynthetic metabolisms were concurrent with a slightly more modern radiocarbon content consistent with inputs from autotrophy using atmospheric carbon.
The second study investigated Dipicolinic Acid (DPA), a biomarker for endospores, a highly resistant state of a variety microbial Genera. This state can survive radiation, desiccation, heat, and bacterivore digestion, and is brought on due to the environment the microbe is living on becoming harsh or unfavorable. Endospores can remain viable for extended periods of time, up to millions of years (Cano & Boruki, 1995; Vreeland, Rosenzweig, & Powers, 2000), which has made them an organism of interest for astrobiology. The presence and potential survivability of endospores within bentonite clay is also of highly applied interest to the Nuclear Waste Management Organization (NWMO) who is proposing to use bentonite within their multi-barrier spent nuclear fuel storage proposal. This study was undertaken to determine the extent of mineral matrices on the effectiveness of DPA extraction from bentonite clay, as well as other planetary analogs. This initial study demonstrated that extraction of DPA was able to effectively identify and quantify the presence of known numbers of spores added to bentonite clay. For this, plates of Bacillus Subtilis were grown and suspended, then cells were counted in a hemacytometer to determine concentration of the spore suspension, which was used to spike mineral matrices to learn how they influence the recovery of DPA during extraction. Further, it showed that the presence of bentonite did not have a significant effect on recovery. The only mineral matrix to see significantly lower than expected recovery was basalt. Finally, initial tests on unseeded bentonite clay showed that spores were below limit of quantification for all samples, but above the limit of detection / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/29742 |
| Date | January 2024 |
| Creators | Pereira, John Christopher |
| Contributors | Slater, Gregory F., Earth and Environmental Sciences |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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