RESUMO
Although a common reaction in anaerobic environments, the conversion of formate and water to bicarbonate and H(2) (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 H(2) consumption by the methanogens, which lowers the H(2) 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 H(2). Here we report that several hyperthermophilic archaea belonging to the Thermococcus genus are capable of formate-oxidizing, H(2)-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.
Assuntos
Formiatos/metabolismo , Hidrogênio/metabolismo , Thermococcus/crescimento & desenvolvimento , Thermococcus/metabolismo , Trifosfato de Adenosina/análise , Trifosfato de Adenosina/biossíntese , Anaerobiose , Biocatálise , Dióxido de Carbono/metabolismo , Elétrons , Formiato Desidrogenases , Perfilação da Expressão Gênica , Regulação da Expressão Gênica em Archaea/genética , Hidrogenase , Liases/metabolismo , Modelos Biológicos , Complexos Multienzimáticos , Família Multigênica/genética , Oxirredução , Pressão Parcial , Prótons , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Thermococcus/classificação , Thermococcus/genética , Água/metabolismoRESUMO
Analysis of the complete genome of Thermococcus sp. strain AM4, which was the first lithotrophic Thermococcales isolate described and the first archaeal isolate to exhibit a capacity for hydrogenogenic carboxydotrophy, reveals a proximity with Thermococcus gammatolerans, corresponding to close but distinct species that differ significantly in their lithotrophic capacities.
Assuntos
Monóxido de Carbono/metabolismo , Genoma Arqueal , Hidrogênio/metabolismo , Sulfetos/metabolismo , Thermococcus/genética , Processos Autotróficos , Sequência de Bases , Temperatura Alta , Dados de Sequência Molecular , Oxirredução , Água do Mar/microbiologia , Thermococcus/isolamento & purificação , Thermococcus/metabolismoRESUMO
We report here the complete sequence and fully manually curated annotation of the genome of strain Ch5, a new member of the piezophilic hyperthermophilic species Thermococcus barophilus.