Terrestrial hot springs have provided a niche space for microbial communities throughout much of Earth’s history, and evidence for hydrothermal deposits on the Martian surface suggest this could have also been the case for the red planet. Prior to the evolution of photosynthesis, life in hot springs on early Earth would have been supported though chemoautotrophy. Today, hot spring geochemical and physical parameters can preclude the occurrence of oxygenic phototrophs, providing an opportunity to characterize the geochemical and microbial components. In the absence of the photo-oxidation of water, chemoautotrophy in these hot springs (and throughout Earth’s history) relies on the delivery of exogenous electron acceptors and donors such as H2, H2 S, and Fe2+. Thus, systems fueled by chemoautotrophy are likely energy substrate-limited and support low biomass communities compared to those where oxygenic phototrophs are prevalent. Low biomass silica-precipitating systems have implications for preservation, especially over geologic time. Here, we examine and compare the productivity and composition of low biomass chemoautotrophic versus photoautotrophic communities in silica-saturated hot springs. Our results indicate low biomass chemoautotrophic microbial communities in Yellowstone National Park are supported primarily by sulfur redox reactions and, while similar in total biomass, show higher diversity in anoxygenic phototrophic communities compared to chemoautotrophs. Our data suggest productivity in Archean terrestrial hot springs may be directly linked to redox substrate availability, and there may be high potential for geochemical and physical biosignature preservation from these communities.
Bibliographical noteFunding Information:
Funding: This work was supported by the University of Minnesota. The authors acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for providing resources that contributed to the research results reported within this paper.
Acknowledgments: T.L.H. and J.R.H. conduct research in Yellowstone National Park under research permit YELL-2018-SCI-7020 issued by the Yellowstone Research Permit Office and reviewed annually. This work was supported by the University of Minnesota. The authors acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for providing resources that contributed to the research results reported within this paper. We are grateful to the entire staff of the Yellowstone Research Permit Office for facilitating the permitting process to perform research in YNP, especially Annie Carlson and Erik Oberg. We thank C. Grettenberger, A. Czaja, A.J. Gangidine, A. Gangidine, J. Kuether, T. Djokic, L. Brengman, L. Seyler, A. Bennett, and A. Rutledge for technical assistance in the field and A. Borowski and P. Swanson for assistance processing samples in the lab. The authors gratefully acknowledge the input of two anonymous reviewers for comments and suggestions that greatly improved this paper.
- Carbon uptake
- Early Earth
- Hot springs
- Low biomass
- Silica precipitating