The class archaeoglobi

Abstract

Archaeoglobaceae, the only family in the class Archaeoglobi, has three genera: Archaeoglobus, Geoglobus, and Ferroglobus. All are thermophilic, obligate anaerobes with highly diverse metabolisms, including chemolithoautotrophy, heterotrophy, sulfate reduction, nitrate reduction, iron reduction, and iron oxidation. Terminal electron acceptors used by the family include sulfur oxyanions, poorly crystalline Fe (III) oxide, humics, and nitrate, while at least 40 different electron donors have been identified (Table 3.1). Motility is observed in all species except Archaeoglobus profundus, Archaeoglobus sulfaticallidus, and Geoglobus acetivorans, and cells are regular to irregular cocci. Analysis of the five sequenced genomes revealed previously unknown metabolic potential that was subsequently targeted by pure culture studies in Archaeoglobus fulgidus. The genomes of A. fulgidus and Ferroglobus placidus are approximately 2.2 Mb, and A. sulfaticallidus is 2.1 Mb, while A. profundus is approximately 1.6 Mb and Archaeoglobus veneficus is 1.9 Mb. The phylogenetic relationships of the species relative to their respective genera have been questioned, and so it has been suggested that additional isolates are necessary to more accurately define the family. Archaeoglobaceae 16S rRNA gene sequences have been detected in both marine and terrestrial hydrothermal systems and oil fields, suggesting that members of the family are widespread in high-temperature environments.