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Although a common reaction in anaerobic environments, the conversion of formate and water to bicarbonate and [H.sub.2] (with a change in Gibbs free energy of ΔG° = + 1.3 kJ [mol.sup.-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 AZ (1). The basis of the sustainable growth of the formate-users is explained by [H.sub.2] consumption by the methanogens, which lowers the [H.sub.2] partial pressure, thus making the pathway exergonic (2). However, it has not been shown that a single strain can grow on formate by catalysing its conversion to bicarbonate and [H.sub.2]. Here we report that several hyperthermophilic archaea belonging to the Thermococcus genus are capable of formate-oxidizing, [H.sub.2]-producing growth. The actual ΔG values for the formate metabolism are calculated to range between -8 and - 20 kJ [mol.sup.-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., Formate-dependent [H.sub.2] production has been previously examined in several prokaryotes, and it is dependent on formate hydrogen lyase systems composed of formate dehydrogenase and membrane-associated hydrogenase (3). In Escherichia coli [...]

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° = +1.3 kJ 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 AZ. 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 exergonic. 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. [ABSTRACT FROM AUTHOR]