The goal of this research was to study the impact of high salinity stress on enrichment cultures containing algae and heterotrophic bacteria from a lake located in the McMurdo Dry Valleys, Antarctica. The research question – Does high salinity stress affect the phylogenetic diversity of microbial communities in a dry valley lake? – tested the hypothesis: phylogenetic diversity of eukaryotes and bacteria will increase when compared to the control group. Lake Bonney is a saline lake, so adding an increased concentration of salt should increase the phylogenetic diversity. This research is relevant to Environmental Microbiology because learning about the diversity of microorganisms helps researchers understand the carbon and nutrient cycling in dry valley lakes. Lake Bonney is permanently covered with ice. The lake has a highly stratified aquatic environment, along with very stable physical conditions. Microbial enrichment cultures were grown from Lake Bonney water, then cultures were inoculated into either high salt stress or control conditions (3 biological replicates for each treatment). The growth progress was monitored and measured over the course of 11 weeks. After the samples were left to grow, cultures were filtered, and environmental DNA was isolated and sequenced for 16S and 18S rRNA. The samples were run through PCR gel electrophoresis and sequenced using Next Generation Sequencing. The results showed that phylogenetic diversity of eukaryotic and bacterial abundance increased in high salinity environments. Most of the eukaryotic organisms present thrived in high salinity environments while some declined, possibly due to having a preference for freshwater environments. The majority of the bacterial organisms present preferred the high salinity environment and increased diversity among the stressed samples. This research allows us to see the full effect of high salinity and its impact on the phylogenetic diversity. Moving forward, we can research the effects of high salinity stress on phylogenetic diversity in other types of lakes worldwide.
Authors: Hannah Loncar and Jo Lebrun
Faculty Advisor: Rachel Morgan-Kiss, Department of Microbiology
Graduate Student Advisor: Chandra Mani Kafle, Department of Microbiology
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