Integrating Geochemistry and (Meta)genomics in the Geothermal Springs in Yellowstone National Park: Mapping the Functional Limits of Life in Early Earth Analog Environments
When: October 17, 2011 11AM PDT
The genetic record of extant microorganisms documents the interactions between life and the environment throughout Earth history. This evolutionary link forms the basis of an emerging area of astrobiology research that is directed at quantifying the relationships between the distribution, diversity, and metabolic composition of microbial life and the characteristics of the environment that it inhabits. The strong physical and chemical gradients and the relatively simple microbial diversity associated with geothermal environments makes them model environments for the development and application of techniques capable of quantifying the extent of such relationships. Our recent results have documented non-random patterns in the spatial distribution of individual genes [e.g., ribosomal (16S rDNA), nitrogenase (nifH), hydrogenase (hydA), chlorophyll biosynthesis (bchL)] in the geothermal springs in Yellowstone National Park (YNP), Wyoming, USA. These results suggested that the microbial populations that harbor these genes have evolved specific physiological traits that enable them to inhabit a particular ecological niche (i.e., multiplicity of chemical and physical parameters that characterize a microenvironment). To further examine this phenomenon and to uncover the traits facilitating niche conservatism in these communities, we investigated the composition of ~30 community metagenomes in YNP using a suite of ecological modeling tools. The results suggest that the metabolic composition of microbial mat communities can be accurately predicted based on the physicochemistry of the environment. Of particular significance is the strict temperature-dependent demarcation noted between the metabolic composition of chemotrophic communities (supported by chemical energy) and phototrophic communities (supported by light energy) as well as the pH-dependent demarcation in the metabolic composition of chemotrophic communities. Additional results from recent modeling and in situ activity-based studies will be presented that reveal the environmental constraints that define the distribution of metabolic processes in these early Earth analog environments. Collectively, these results provide clues as to the parameters that drove the evolution of metabolic processes on Earth and also serve as a foundation for predicting the habitability of early Earth environments and newly discovered extraterrestrial planetary bodies.