The Geoglobus acetivorans Genome: Fe(III) Reduction, Acetate Utilization, Autotrophic Growth, and Degradation of Aromatic Compounds in a Hyperthermophilic Archaeon

<jats:title>ABSTRACT</jats:title> <jats:p> <jats:named-content content-type="genus-species">Geoglobus acetivorans</jats:named-content> is a hyperthermophilic anaerobic euryarchaeon of the order <jats:named-content content-type="genus-species">Archaeoglobales</jats:named-content> isolated from deep-sea hydrothermal vents. A unique physiological feature of the members of the genus <jats:named-content content-type="genus-species">Geoglobus</jats:named-content> is their obligate dependence on Fe(III) reduction, which plays an important role in the geochemistry of hydrothermal systems. The features of this organism and its complete 1,860,815-bp genome sequence are described in this report. Genome analysis revealed pathways enabling oxidation of molecular hydrogen, proteinaceous substrates, fatty acids, aromatic compounds, <jats:italic>n</jats:italic> -alkanes, and organic acids, including acetate, through anaerobic respiration linked to Fe(III) reduction. Consistent with the inability of <jats:named-content content-type="genus-species">G. acetivorans</jats:named-content> to grow on carbohydrates, the modified Embden-Meyerhof pathway encoded by the genome is incomplete. Autotrophic CO <jats:sub>2</jats:sub> fixation is enabled by the Wood-Ljungdahl pathway. Reduction of insoluble poorly crystalline Fe(III) oxide depends on the transfer of electrons from the quinone pool to multiheme <jats:italic>c</jats:italic> -type cytochromes exposed on the cell surface. Direct contact of the cells and Fe(III) oxide particles could be facilitated by pilus-like appendages. Genome analysis indicated the presence of metabolic pathways for anaerobic degradation of aromatic compounds and <jats:italic>n</jats:italic> -alkanes, although an ability of <jats:named-content content-type="genus-species">G. acetivorans</jats:named-content> to grow on these substrates was not observed in laboratory experiments. Overall, our results suggest that <jats:named-content content-type="genus-species">Geoglobus</jats:named-content> species could play an important role in microbial communities of deep-sea hydrothermal vents as lithoautotrophic producers. An additional role as decomposers would close the biogeochemical cycle of carbon through complete mineralization of various organic compounds via Fe(III) respiration. </jats:p>