PhD candidate – Dept. of Microbiology and Immunology
Montana State University
Bio:
Melody Lindsay is a 3rd year doctoral student in Dr. Eric Boyd’s geobiology lab in the Department of Microbiology and Immunology at Montana State University. Ms. Lindsay studies the distributions and activities of extremophiles, with the goal of further characterizing the physiological adaptations that facilitate life under extreme conditions. Her primary thesis project is directed at identifying the influence that geological hydrogen has on the distribution and diversification of (hyper)thermophilic organisms and their hydrogenase enzymes in hot spring environments present in Yellowstone National Park. She has also worked on several projects focused on the microbialites and associated microbial communities that inhabit her other favorite field location which is Great Salt Lake, Utah. Using next generation sequencing techniques and physiological assays, her work in GSL is aimed at characterizing the community composition of microbialite microorganisms, identifying the active architects of the structures, and their role in supporting the GSL ecosystem.
Title: Molecular Characterization of Microbialites in Great Salt Lake, Utah
11:15am - Wednesday, May 11th
Abstract: A railroad causeway constructed in 1959 across Great Salt Lake, Utah, has restricted water flow into the northern portion of the Lake, resulting in a higher salinity North Arm (NA, 31.4% salinity) and a lower salinity South Arm (SA, 11.8% salinity). Carbonate microbialite structures were collected from the NA and the SA for use in evaluating the effect of increased salinity on their mineralogy and the abundance and composition of associated microbial communities. These samples also permitted analyses leading to the identification of the likely architects of SA microbialites and a direct comparison with their distribution in NA microbialites. Quantitative molecular analysis of the abundance of 16S and 18S rRNA genes indicates that the SA microbialites harbor significantly more biomass than the NA microbialites, indicating that the former are more productive. Characterization of the taxonomic (16S and 18S rRNA) and functional (Geochip microarray) gene diversity of SA and NA microbialite communities reveal distinct differences. In particular, an abundance of sequences affiliated with photoautotrophic cyanobacteria and diatoms were identified in the SA microbialite which may be involved in carbonate precipitation; these photoautotrophic taxa were not identified in the NA microbialite. Microspar calcite was also identified in the SA microbialite, which has been interpreted to be the result of biological precipitation.
To further characterize the SA microbialite communities, we sequenced and quantified transcripts of taxonomic (16S and 18S rRNA) genes extracted from microbialites sampled over a day/night cycle. These results reveal a significant shift in the abundance and composition of the active fraction of the communities. Quantitative analysis indicates increases in total transcript abundances at 2AM and 2PM. Community composition analyses also indicate the presence of the same photosynthetic populations previously identified by 16S and 18S rRNA gene sequencing. This indicates that the previously identified potential architects of SA microbialites are active in these systems. In addition, preliminary analyses used to quantify primary productivity in microbialites incubated in the light and the dark demonstrate an increase in light-driven primary productivity within microbialite associated communities. Collectively, we interpret these observations to indicate that NA microbialites are remnant features and indicate that the associated communities are no longer actively precipitating carbonate minerals. Moreover, the results suggest a role for active photoautotrophic cyanobacteria and diatoms in the formation of GSL SA microbialites and in the primary productivity of GSL.