An organic geochemical investigation into lipid distribution at Imperial Geyser, Yellowstone National Park
Abstract
Imperial Geyser, Yellowstone National Park, is an alkaline, silica-rich thermal spring with a diverse microbial constituency. In order to characterize this microbial community, mat samples growing downstream from the vent were studied for lipid composition and abundance. Both fatty acids and hopanoids were extracted from the mat samples and analyzed using GC-MS and GC-FID. Microbial community profiling was also performed targeting the 16S rRNA gene and the SHC (squalene-hopene cyclase) gene. Results for both lipid and metagenomic data were compared using principle components analysis (PCA). PCA revealed the clustering of sample sites for both lipids and genes. A strong correlation (p value < .01) between lipid composition and phylogenetic composition per sample was observed. Procrustes analysis also showed a strong correlation between hopanoid abundance and phylogenetic composition (p=0.005). A correlation was also seen between relative abundances of C15 and a-C17 fatty acids with genetic data of Chloroflexus and Chlorobium, indicating that they are the likely source of these lipids at Imperial Geyser. Hopanoid data shows the ratio of methylated to unmethylated hopanoids varies with distance from the vent, potentially representing a response to environmental stress. The ratio of methylated to unmethylated hopanoids appears to be controlled environmentally, being produced by organisms beyond Cyanobacteria. Thus in this setting the 2-methylhopanoid index does not correspond directly to the relative abundance of Cyanobacteria. Results indicate that temperature and pH exert some control over community composition between sample sites and that this is reflected in the lipid composition. However, we also expect to see additional geochemical variants, such as dissolved inorganic carbon, nitrogen, phosphorous, and sulfur from the stream water, contributing to the beta diversity of our results. This research was undertaken as part of the International Geobiology Course 2011.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.B51G0493B
- Keywords:
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- 0410 BIOGEOSCIENCES / Biodiversity;
- 0448 BIOGEOSCIENCES / Geomicrobiology;
- 0456 BIOGEOSCIENCES / Life in extreme environments