A preliminary analysis of the lipid contents of a biofilm from a Yellowstone hydrothermal pool

Abstract

The hot springs at Yellowstone National Park, such as Obsidian Pool, have been extensively studied as a source for previously unidentified microorganisms. Most of the previous studies focused on the genomic diversity of these environments, but recent interest in environmental samples for the study of lipid biomarkers has extended to these hot springs as well. In this preliminary study of Obsidian Pool, I used a modified Bligh and Dyer extraction process to create a total lipid extract (TLE), which was then further separated and processed by an acetone precipitation, mild alkaline methanolysis and column chromatography to isolate different fractions of the TLE. Compounds were then identified by gas chromatography-mass spectrometry (GCMS). The mild alkaline methanolysis allowed for the identification of decanoic acid methyl ester, a fatty acid methyl ester. From the column chromatography, only the saturated hydrocarbon fraction yielded interesting compounds; these were a series of n-alkanes (n-C₁₇, n-C₂₀, and n-C₂₃ - n-C₃₁), two branched alkanes (5-methyloctodecane and 4-methylheptadecane), an isoprenoid (dibiphytane), a series of branched aliphatic alkanes with a quaternary substituted carbon atom (5,5 diethylalkanes), and a variety of hopanoids and steroids. These compounds indicate a strong community of bacterial and archaeal species in Obsidian pool. Some compounds that were indicative of eukarya were also identified, although a more in-depth study is necessary to determine whether these signals were from the pool or from external inputs. The lipids identified in this study indicate that the genomic diversity established by previous studies is reflected in the lipid diversity of Obsidian Pool. However, more study is required to fully categorize the lipids in the pool.