Antarctic ecosystems are one of the few places where mankind has yet to significantly disturb the biogeochemical cycling of microorganisms. The goal of this study was to subject samples from Lake Fryxell, an Antractic freshwater lake, to high salinity conditions in order to observe compositional changes in the microbial communities and detect resilience. We conducted biometric assessments to determine photosynthetic activity and density of the mixed communities following exposure to salinity. Cultures were then filtered for DNA extraction to generate samples for DNA amplification using the polymerase chain reaction (PCR). These products were then sequenced for 16S/18S rRNA to generate a catalog of detectable taxonomic units indicating the microbial succession following salt exposure. Significantly lower optical density values and cell counts per mL compared to normal salinity controls indicated that high salinity conditions inhibited proliferation of the mixed culture at 4 weeks and likely decreased the survivability of several species. Photosynthetic activity was less significantly affected, indicated by relatively stable chlorophyll fluorescence values compared to t(0). In an additional experiment, novel Antarctic bacteria were cultured on Petri dishes and streaked for isolation. All bacteria were found to be psychrotolerant. Overall, the knowledge that salinity decreased survivability and proliferation in the mixed culture provides information about the relationship between microbial communities and abiotic environmental factors. Future investigations may sample cultures at multiple time points to determine how the community structure changes as it matures. Metabolic studies of the bacteria and protists present in the samples would also provide more insight into potential community interactions. Overall, this experience has helped us develop hypotheses and analyze data critically to draw conclusions, as well as taught us commonly used research methods. These are skills that will continue to serve us as we move forward to medical school and graduate studies respectively.
Authors: Gabriel Ortiz, Matty Weaver
Faculty Advisor: Rachael Morgan-Kiss, Microbiology
Graduate Student Advisors: Chandramani Kafle, Microbiology | Drew Wolf, Microbiology
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