Microbial Ecosystem in Deep-Sea Hydrothermal Systems

Over the past 40 years, researchers have explored deep-sea and subseafloor environments around the globe and studied a number of microbial ecosystems, sometime called as Dark Energy Ecosystems. Multi-omics and interdisciplinary approaches have recently provided new insights into the compositional and functional diversity of microbial life living in the dark world. It is now evident that the most fundamental driving force is chemical disequilibrium at a given habitat, which controls the outline of microbial community, in particular, the magnitude and mode of chemolithotrophic primary production and the subsequent biogeochemical energy and element cycles. 

This was originally predicted by a thermodynamic calculation of energy mass balance of chemolithotrophic metabolisms in a simulated deep-sea hydrothermal vent environment. The prediction, called as McCollom and Shock’s prediction, has been later justified by a number of microbiological studies in various deep-sea hydrothermal vent environments all over the world. Once the prediction could be realized as a principle, the principle can be applied not only to understanding of dark energy ecosystems other than in deep-sea hydrothermal vents but also to reconstruction of the most ancient ecosystem in the Earth and even to searching the possible extraterrestrial ecosystems in our solar system.

On the other hand, recent geoelectrochemical studies of deep-sea hydrothermal environments have revealed that the chemical disequilibrium can drive not only the chemolithotrophic primary production but also the possible electrotrophic primary production and even abiotic electrosynthesis. They represent a new aspect of Dark Energy Ecosystems and may be key processes to origin of earthly life.