Comprehensive Longitudinal Analysis of the Five Sisters Hot Springs in Yellowstone National Park Reveals a Dynamic Thermoalkaline Environment

Abstract Research focused on microbial populations of thermoalkaline springs has been driven in a large part by the lure of discovering functional enzymes with industrial applications in high-pH and high temperature environments. However, the fundamental ecology of these springs has largely been overlooked. To better understand the functional outcomes of interactions between the geochemistry and the microbial community of thermoalkaline springs, we conducted a three-year study of the Five Sisters (FS) springs that included high-resolution geochemical measurements, 16S rRNA sequencing of the bacterial and archaeal community, and mass spectrometry based extracellular and intracellular small molecule characterization. By combining all four datasets, we completed a comprehensive analysis of the intricate thermoalkaline spring system. Over the course of the study, the microbial population responded to changing environmental conditions, with archaeal populations decreasing in both relative abundance and diversity when compared to bacterial populations. Decreases in the relative abundance of Archaea were associated with environmental changes that included decreased availability of specific nitrogen and sulfur containing extracellular small molecules. The multi-factorial analysis suggests a complex and dynamic environment with an elastic microbial community that responded to geochemical and extracellular small molecule transitions.