DATE2025.02.04 #Press Releases
Utilizing JAEA's underground research facilities to elucidate the function of unknown microorganisms underground
-Estimating the Long-Term Stability of Subsurface Environments from Microbial Communities-
Summary
This study revealed that a very high percentage of unknown microorganisms are present in deep subsurface granite and sedimentary rock environments, and that representative metabolic reactions are common to both environments, despite the differences in microbial communities in the two environments. In addition, about one-third of the microbial genomes detected in the subsurface environment of the studied sedimentary rocks were almost identical, suggesting the possibility of understanding the stability of the subsurface environment from the microbial community.
Although there is an abundance of microorganisms deep underground, many of them are unknown microorganisms that have never been cultured, and there remain many unresolved aspects of their underground functions. For the utilization of underground space, such as for the geological disposal of high-level radioactive waste, it is important to deepen our understanding of the phenomena related to microorganisms living underground.
In this study, we utilized JAEA's underground research facilities (Mizunami and Horonobe), which were constructed to study two types of rock masses, granite and sedimentary rock. Microorganisms in groundwater at depths of 140 to 400 m were monitored for up to four years using a method called "metagenomic analysis," which analyzes the genome of the entire community, to comprehensively analyze microbial communities and metabolic reactions. As a result, despite the marked differences between the microbial communities of granite and sedimentary rocks, the metabolic reactions of hydrogen, carbon dioxide ( CO2 ), nitrogen, sulfur, and methane were identified as common and representative metabolic reactions. In particular, the metabolic activity in the sedimentary rock basement of Horonobe is attributed to the abundance of organic matter, CO2 and iron.
Almost identical microbial genomes were detected in about one-third of the groundwater samples from various depths in Horonobe, indicating that microorganisms with identical genomes are distributed at different depths in the subsurface. This indicates that part of the microbial community in the deep subsurface of Horonobe migrated from the surface during the last glacial period (about 70,000 to 10,000 years ago) or earlier, when groundwater flowed relatively easily to the deep subsurface, and that the microbial community has been distributed from the end of the last glacial period (about 10,000 years ago), when groundwater flow became very slow due to subsequent environmental changes, to the present. This indicates the possibility that the migration was restricted deep underground for a long period of time from the end of the last glacial period (about 10,000 years ago) to the present, when the flow of groundwater slowed down significantly due to subsequent environmental changes.
The characteristics of the microbial community in the sedimentary rock basement indicate that the slow groundwater flow is geochemically very stable, which is important not only for geological disposal of high-level radioactive waste, but also for underground storage of hydrogen and CO This is expected to be used as important knowledge not only for geological disposal of high-level radioactive waste but also for technologies to utilize underground space for underground storage of hydrogen and CO2
This research was conducted by a research team led by Associate Managing Director Yuki Amano of the BE Resource and Disposal Systems Development Department, Nuclear Fuel Cycle Engineering Laboratories, Japan Atomic Energy Agency (Executive Vice President Masanori Koguchi), a research group led by Professor Gillian Banfield of the University of California, Berkeley, and a research group led by Associate Professor Yohei Suzuki of the Graduate School of Science, The University of Tokyo. Associate Professor Yohey Suzuki of The University of Tokyo.
The research results were published online in the international journal Environmental Microbiome on December 18, 2024.
Figure: Conceptual diagram of groundwater flow in the Horonobe area and microorganisms present in the groundwater.
links: Japan Atomic Energy Agency (JAEA)
Journals
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Journal name Environmental MicrobiomeTitle of paper