The Hydrogenophilaceae are a family of the

Hydrogenophilalia The class Hydrogenophilalia in the '' Bacteria'' was circumscribed in 2017 when it was demonstrated that the order '' Hydrogenophilales'' was distinct from the ''Betaproteobacteria'' on the basis of physiology, biochemistry, fatty acid profiles, ...

, with two genera – '' Hydrogenophilus'' and '' Tepidiphilus''. Like all ''

Pseudomonadota Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. The renaming of phyla in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. Th ...

'', they are

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

. All known species are

thermophilic A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...

, growing around 50 °C and using molecular

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...

or organic molecules as their source of electrons to support growth - some species are

autotroph An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Wo ...

s. The genus ''

Thiobacillus ''Thiobacillus'' is a genus of Gram-negative Betaproteobacteria. ''Thiobacillus thioparus'' is the type species of the genus, and the type strain thereof is the StarkeyT strain, isolated by Robert Starkey in the 1930s from a field at Rutgers Un ...

'' was previously considered to be a member in this family but was reclassified into the order ''

Nitrosomonadales The NitrosomonadalesBoden, R; Hutt, LP, Rae AW (2017) Reclassification of ''Thiobacillus aquaesulis'' (Wood & Kelly, 1995) as ''Annwoodia aquaesulis'' gen. nov., comb. nov., transfer of ''Thiobacillus'' (Beijerinck, 1904) from the ''Hydrogenophil ...

'' at the same time that the ''

Hydrogenophilales The Hydrogenophilaceae are a family of the Hydrogenophilalia, with two genera – '' Hydrogenophilus'' and '' Tepidiphilus''. Like all ''Pseudomonadota'', they are Gram-negative. All known species are thermophilic, growing around 50 °C and ...

'' were removed from the ''

Betaproteobacteria Betaproteobacteria are a class of Gram-negative bacteria, and one of the eight classes of the phylum Pseudomonadota (synonym Proteobacteria). The ''Betaproteobacteria'' are a class comprising over 75 genera and 400 species of bacteria. Togeth ...

'' and the class ''

'' was formed. '' Hydrogenophilus thermoluteolus'' is a facultative

chemolithoautotroph A lithoautotroph is an organism which derives energy from reactions of reduced compounds of mineral (inorganic) origin. Two types of lithoautotrophs are distinguished by their energy source; photolithoautotrophs derive their energy from light while ...

originally isolated from a

hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...

; however, it was detected 2004 in ice core samples retrieved from a depth around 3 km within the ice covering

Lake Vostok Lake Vostok (russian: озеро Восток, ''ozero Vostok'') is the largest of Antarctica's almost 400 known subglacial lakes. Lake Vostok is located at the southern Pole of Cold, beneath Russia's Vostok Station under the surface of the cen ...

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

. The presence of DNA from (and potentially live cells of) thermophilic bacteria in the ice suggests that a geothermal system could exist beneath the cold water body of Lake Vostok, or simply that non-thermophilic strains of '' Hydrogenophilus'' exist and were present in the ice.

References

{{Taxonbar, from=Q134834 Hydrogenophilales Hydrogenophilalia