Characterizing and Evaluating the Diverse Microbial Communities and Their Mercury Resistance Potential from Hot Spring Sites Representing Gradients in Temperature and pH in Yellowstone National Park

Abstract

Yellowstone National Park is home to many different hot springs, lakes, geysers, pools, and basins that range in pH, chemical composition, and temperature. These different environmental variations provide a broad range of conditions that select and grow diverse communities of microorganisms. In this study, we collected samples from geochemically diverse lakes and springs to characterize the microbial communities present through 16S rRNA metagenomic analysis. This information was then used to observe how various microorganisms survive in high mercury environments. The results show the presence of microorganisms that have been studied in previous literature. The results also depict gradients of microorganisms including thermophilic bacteria and archaea that exist in these extreme environments. In addition, beta diversity analyses of the sequence data showed site clustering based primarily on temperature instead of pH or sample site, suggesting that while pH, temperature, and sample site were all shown to be significant, temperature is the strongest factor driving microorganism community development. While it is important to characterize the microorganism community present, it is also important to understand how this community functions as a result of its selection. Along with looking at community composition, genomic material was tested to see if it contained mercury methylating (hgcA) or mercury reducing (merA) genes. Out of 22 samples, three of them were observed to have merA genes, while no samples had hgcA genes. These results indicate that microorganisms in Mustard and Nymph Springs may use mercury reduction. Understanding how microorganisms survive in environments with high concentrations of toxic pollutants is crucial because it can be used as a model to better understand mechanisms of resistance and the biogeochemical cycle, as well as for bioremediation and other solutions to anthropogenic problems.