17:15 〜 18:45
[BCG07-P05] Cerium hyper-enrichment in mineralized microbial structures on ferromanganese crust
Cerium (Ce) is an ultratrace metal, which has sensitively recorded the ocean redox state
throughout the Earth’s history. As the Ce concentration is extremely low, it remains
largely unknown how the behavior of Ce is influenced by microbial activities. Ce is
highly enriched in ferromanganese crust, which extensively covers the seafloor as a major
deep-sea metal resource. Thus, the investigation of ferromanganese crust has a great
potential to unveil Ce-microbe interactions that control the concentration of Ce in the
ocean. In this study, we applied state-of-the-art nanosolid characterization techniques,
which provide here the first glimpse of microbial processes that result in the anomalous
enrichment of Ce near the ferromanganese crust surface. Unexpectedly, Ce is associated
with dead microbial cells biomineralized with heavy metals including Ce as the trivalent
state. Given that Ce(III) is well established to be soluble and mobile in the ocean, the
opposite behavior of Ce(III) was revealed by our study. This new microbial process
leading to Ce(III) fixation has a profound impact for reconstructing the ocean oxygenation
in geologic time, as well as understanding of the present ocean health. In addition,
mineralized microbial cells unveiled here will be hunted for the detection of life on
ancient Earth and Mars.
throughout the Earth’s history. As the Ce concentration is extremely low, it remains
largely unknown how the behavior of Ce is influenced by microbial activities. Ce is
highly enriched in ferromanganese crust, which extensively covers the seafloor as a major
deep-sea metal resource. Thus, the investigation of ferromanganese crust has a great
potential to unveil Ce-microbe interactions that control the concentration of Ce in the
ocean. In this study, we applied state-of-the-art nanosolid characterization techniques,
which provide here the first glimpse of microbial processes that result in the anomalous
enrichment of Ce near the ferromanganese crust surface. Unexpectedly, Ce is associated
with dead microbial cells biomineralized with heavy metals including Ce as the trivalent
state. Given that Ce(III) is well established to be soluble and mobile in the ocean, the
opposite behavior of Ce(III) was revealed by our study. This new microbial process
leading to Ce(III) fixation has a profound impact for reconstructing the ocean oxygenation
in geologic time, as well as understanding of the present ocean health. In addition,
mineralized microbial cells unveiled here will be hunted for the detection of life on
ancient Earth and Mars.