New Mexico Geological Society Annual Spring Meeting — Abstracts

Although microbial studies in hot spring environments are numerous, widespread surveys of the microbial diversity of thermal features are lacking. Many studies of hot spring environments have focused on a single organism or type of spring. In order to expand our knowledge of the extent of thermophilic life, we conducted a microbial inventory of thermal features in Yellowstone National Park that included in-depth geochemical measurements. We have analyzed microbial communities from greater than 40 thermal features from across YNP by 16S rRNA gene analysis of environmental DNA. These samples span the range of temperature and pH (48.9 - 86.2°C and 2.00 – 9.19) encountered in the park’s thermal features. By combining phylogenetic analyses with geochemical data, we attempt to determine the level of control that the geochemistry of a spring exerts on the microbial communities. The relationship between community and geochemistry is strongest when the microbial communities are compared at the genus level. Temperature and pH are correlated with community structure, but do not alone predict the type of organisms present in a spring. Additional geochemical controls include both putative metabolically informative compounds (i.e. SO⁼₄ and NH⁺₄) and trace elements (i.e. F, Sr, Sb). Our geochemical approach includes computation of the state of disequilibrium for coupled redox reactions that represent possible energy-yielding reactions for microbial metabolism. Often, the highest energy yields are for hydrogen and sulfur oxidation: both pathways are known to be employed by Aquificales which dominate many of the sampled springs. Our ongoing work pairs communities with site-specific energy-yield characteristics. These results suggest niche control over community structure at the genus level. However, the much weaker relationship between geochemistry and species level groups suggests other mechanisms such as dispersal between springs or in situ evolution or mutation is affecting the individual populations that comprise the communities.