Yun Jae Kim^1*, Hyun Sook Lee^1,2*, Eun Sook Kim^1*, Seung Seob Bae^1,2*, Jae Kyu Lim^1,2, Rie Matsumi³, Alexander V. Lebedinsky⁴, Tatyana G. Sokolova⁴, Darya A. Kozhevnikova⁴, Sun-Shin Cha^1,2, Sang-Jin Kim^1,2, Kae Kyoung Kwon^1,2, Tadayuki Imanaka³, Haruyuki Atomi³, Elizaveta A. Bonch-Osmolovskaya⁴, Jung-Hyun Lee^1,2 & Sung Gyun Kang^1,2

¹Korea Ocean Research & Development Institute, PO Box 29, Ansan 425-600, Korea. ²Department of Marine Biotechnology, University of Science and Technology, Daejeon 305-333, Korea. ³Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan. ⁴Winogradsky Institute of Microbiology, Russian Academy of Sciences, Prospect 60-Letiya Oktyabrya 7/2, 117312, Moscow, Russia.

Although a common reaction in anaerobic environments, the conversion of formate and water to bicarbonate and H₂ (with a change in Gibbs free energy of ΔG° = +1.3kJ mol^-1) has not been considered energetic enough to support growth of microorganisms. Recently, experimental evidence for growth on formate was reported for syntrophic communities of Moorella sp. strain AMP and a hydrogen-consuming Methanothermobacter species and of Desulfovibrio sp. strain G11 and Methanobrevibacter arboriphilus strain AZ¹. The basis of the sustainable growth of the formate-users is explained by H₂ consumption by the methanogens, which lowers the H₂ partial pressure, thus making the pathway exergonic². However, it has not been shown that a single strain can grow on formate by catalysing its conversion to bicarbonate and H₂. Here we report that several hyperthermophilic archaea belonging to the Thermococcus genus are capable of formate-oxidizing, H₂-producing growth. The actual ΔG values for the formate metabolism are calculated to range between -8 and -20 kJ mol ^-1 under the physiological conditions where Thermococcus onnurineus strain NA1 are grown. Furthermore, we detected ATP synthesis in the presence of formate as a sole energy source. Gene expression profiling and disruption identified the gene cluster encoding formate hydrogen lyase, cation/proton antiporter and formate transporter, which were responsible for the growth of T. onnurineus NA1 on formate. This work shows formate-driven growth by a single microorganism with protons as the electron acceptor, and reports the biochemical basis of this ability.