Presentation Information
[U17-09]Electricity utilization by electroactive Shewanella sp. EC-1 isolated from a deep-sea hydrothermal field
*Masahiro Yamamoto1 (1.Japan Agency for Marine-Earth Science and Technology)
Keywords:
deep-sea hydrothermal field,electroactive bacteria,extracellular electron transfer
The “electrochemical evolution theory”, in which electricity generated from deep-sea hydrothermal field droved the prebiotic anabolic metabolisms on the early Earth, has been proposed. If primitive metabolisms were driven by electricity from deep-sea hydrothermal fields, the electrical energy would have continued to be an effective energy source for microbial cells in the subsequent biological evolution. We have suggested the existence of electroactive microorganisms utilizing electrical discharges from modern deep-sea hydrothermal vents. In this study, we report the electroactivity of a bacterial strain isolated from a deep-sea hydrothermal field.
A highly conductive rock sample collected from a deep-sea hydrothermal field was used as a microbial inoculant and the working electrode in a microbial electrochemical cultivation system in laboratory, simulating the electrical discharge observed at deep-sea hydrothermal fields. We observed enrichment of Shewanella bacteria in the culture medium, and isolated Shewanella sp. strain EC-1 from the culture by dilution plating. The determined genome of strain EC-1 revealed that it contained a gene cluster encoding the metal reduction (Mtr) pathway like many other Shewanella bacteria, suggesting that strain EC-1 is an electroactive bacterium. Electrochemical measurements of EC-1 cells revealed electron transfer between the cells and the electrode, suggesting that the strain performs extracellular electron transfer. Electrochemical cultivations of EC-1 at different potentials and changes in the current were monitored. The results suggest that bidirectional extracellular electron transfer between the electrode and the cells. A range of potentials has been observed on the seafloor at deep-sea hydrothermal fields, suggesting that strain EC-1 has the ability to both absorb and emit electricity in the natural environment.
This work suggests that electrical energy can be used as an option for supporting life in deep-sea hydrothermal fields, and indicates a new means of energy harvesting for microorganisms in natural environments.
A highly conductive rock sample collected from a deep-sea hydrothermal field was used as a microbial inoculant and the working electrode in a microbial electrochemical cultivation system in laboratory, simulating the electrical discharge observed at deep-sea hydrothermal fields. We observed enrichment of Shewanella bacteria in the culture medium, and isolated Shewanella sp. strain EC-1 from the culture by dilution plating. The determined genome of strain EC-1 revealed that it contained a gene cluster encoding the metal reduction (Mtr) pathway like many other Shewanella bacteria, suggesting that strain EC-1 is an electroactive bacterium. Electrochemical measurements of EC-1 cells revealed electron transfer between the cells and the electrode, suggesting that the strain performs extracellular electron transfer. Electrochemical cultivations of EC-1 at different potentials and changes in the current were monitored. The results suggest that bidirectional extracellular electron transfer between the electrode and the cells. A range of potentials has been observed on the seafloor at deep-sea hydrothermal fields, suggesting that strain EC-1 has the ability to both absorb and emit electricity in the natural environment.
This work suggests that electrical energy can be used as an option for supporting life in deep-sea hydrothermal fields, and indicates a new means of energy harvesting for microorganisms in natural environments.