Our oldest national park may hold answers to fundamental scientific questions about the activities of microbial communities that, in turn, may help in developing bioenergy technologies or safely storing carbon dioxide.
Detailed analyses of metagenome assemblies by scientists at Montana State University, the Department of Energy's (DOE) Pacific Northwest National Laboratory (PNNL), the DOE Joint Genome Institute (JGI), and Indiana University have revealed a new archaeal phylum in microbial mats from Yellowstone National Park (YNP) hot springs. The work was published online by The ISME Journal.
The research is part of a DOE program led by PNNL called Biological Systems Interactions. "Our overall objective is to support DOE's goal of gaining a predictive understanding of microbial communities by studying microbial mat systems," said Dr. Margie Romine, PNNL. "These systems are metabolically interactive, self-sustaining biological systems that are widespread in saline and thermal aquatic environments."
Archaea comprise one of the three domains of life. This group includes microorganisms that can survive in extreme environmental conditions, such as those found in hot springs at YNP. A phylum is the taxonomic rank below the domain level, and to date, only five archaeal phyla have been confirmed.
The newly proposed candidate phylum, Geoarchaeota, is represented by a novel archaeal population found in outflow channels of YNP. Replicate metagenome assemblies of the newly described organism appear to bridge phylogenetic gaps among other phyla within the domain.
"Previous studies of acidic ferric iron mats from Yellowstone had shown a remarkable diversity of uncultivated, undescribed archaea," said Dr. Bill Inskeep, Montana State University. "One of our goals was to identify and describe novel thermophilic—requiring high temperature—archaea inhabiting microbial mats in YNP."
The microbial mats are chemotrophic, meaning they obtain energy by mediating geochemical reactions such as oxidizing inorganic compounds present in geothermal waters. In this specific case, the mats oxidize ferrous iron, resulting in the production of rust-colored ferric iron oxides.
The geothermal systems in YNP are field laboratories for scientists who want to understand the origin and evolution of metabolic processes necessary for life in extreme environments. Such microbial communities carry out critical ecosystem services, including energy capture, carbon fixation, and biogeochemical cycling of nutrients and metals, and are being harnessed for studying engineered systems potentially useful for bioenergy and carbon sequestration.
This discovery shows the power of sequencing DNA directly from the environment, or metagenomics, to discover and characterize previously unknown microbes present in unusual niches. Identification of these novel organisms is critical to understanding the structure and function of thermophilic mat microbial communities and will give insight to the evolution of archaea in early Earth environments that may have important analogs in YNP today.
The scientists extracted DNA for metagenome sequencing from iron-oxide microbial mats from YNP's One-Hundred Spring Plain located in Norris Geyser Basin. They performed phylogenetic analyses on the resulting deduced protein sequences as well as detailed comparative analysis to other known archaea genomes.
Scientists at Montana State University are attempting to cultivate the first member of the proposed phylum Geoarchaeota. In collaboration with scientists at PNNL they hope to develop a better understanding of the role of this organism in iron-oxidizing mats, focusing on its interactions with Metallosphaera yellowstonesis MK-1, the dominant chemoautotroph responsible for fixing carbon in this mat environment.
The work conducted by PNNL and DOE JGI was sponsored by the Office of Biological and Environmental Research within DOE's Office of Science. Additional support was provided by NASA Exobiology, the National Science Foundation Integrative Research and Graduate Training Program, and the Montana Agricultural Experiment Station.
The Department's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information please visit http://science.energy.gov/about. For more information about Pacific Northwest National Laboratory, please go to: http://www.pnnl.gov/.
Julie Wiley is a Senior Communications Specialist in the Biological Sciences Division at PNNL