The family hydrogenothermaceae

Abstract

Hydrogenothermaceae, a family within the order Aquificales and the phylum Aquificae, embraces the genera Hydrogenothermus, Persephonella, Sulfurihydrogenibium, and Venenivibrio. All the strains of the family Hydrogenothermaceae are thermophilic and optimally grow at a temperature range of 65-73 °C. The genera Hydrogenothermus and Persephonella consist of the strains that are isolated from submarine hydrothermal systems and represent halophily equivalent to NaCl concentrations in their marine habitats, while all the strains of the genera Sulfurihydrogenibium and Venenivibrio are isolated from terrestrial freshwater geothermal systems and do not require NaCl for their growths. This niche preference is obviously a watershed of the phylogenetic relationship among the members of the family Hydrogenothermaceae, and the family Hydrogenothermaceae is phylogenetically classified further into the subfamilies of Hydrogenothermus/Persephonella and Sulfurihydrogenibium/Venenivibrio groups. Most of the species within the Hydrogenothermaceae are strictly chemolithoautotrophs that utilize H2, S0, and thiosulfate as electron donors and O2 and nitrate as electron acceptors. However, several strains show highly versatile energy and carbon metabolic capabilities such as iron (II) oxidation, arsenite oxidation, S0 reduction, iron (III) reduction, arsenate reduction, selenite reduction, and heterotrophy with various complex organics and organic acids. The complete and draft genome sequences of some Hydrogenothermaceae strains are determined and characterized. The genetic repertoires are highly relevant with their habitat preference, metabolic and physiological capabilities, and evolutionary traits.