Nine pure cultures of neutrophilic haloaloarchaea capable of anaerobic growth by carbohydrate dependent sulfur respiration were isolated from hypersaline lakes in southwestern Siberia and southern Russia. According to phylogenomic analysis the isolates were closely related to each other and formed a new species within the genus Halapricum (family Haloarculaceae). They have three types of catabolism: fermentative, resulting in H2 formation; anaerobic respiration using sulfur compounds as e-acceptors and aerobic respiration. Apart from elemental sulfur, all isolates can also use three different sulfoxides as acceptors and the type strain also grows with thiosulfate, reducing it partially to sulfide and sulfite.
All strains utilized sugars and glycerol as the e-donors and C source for anaerobic growth and some can also grow with alpha-glucans, such as starch and dextrins. The major respiratory menaquinones are MK-8:8 and MK-8:7, but 5–19% consists of ‘‘thermoplasmata” quinones (MMK-8:8 and MMK-8:7), whose occurrence in haloarchaea is unprecedented. On the basis of their unique physiological properties and results of phylogenomic analysis, the isolates are suggested to be classified into a novel species Halapricum desulfuricans sp. nov. (type strain HSR12-2T = JCM 34032T = UNIQEM U1001T).@en

Thi.o.ha.lo’phi.lus. Gr. neut. n. thion sulfur; Gr. masc. n. hals, halos salt of the sea; Gr. masc. adj. philos loving; N.L. masc. n. Thiohalophilus sulfur and salt loving.
The genus Thiohalophilus was originally classified as an unaffiliated member of the Gammaprotebacteria. It is a moderately halophilic, neutrophilic
chemolithoutotroph utilizing reduced sulfur compounds, including sulfide, thiosulfate, and thiocyanate, as the energy source and electron donors and O2 or nitrite (but not nitrate) as the electron acceptors. CO2 is assimilated via the Calvin–Benson–Bassham cycle. The genus includes a single species Thiohalophilus thiocyanatoxydans corrig., which is the type species. Habitat – hypersaline lakes. DNA G+C content (mol%): 57.4 (genome).Type species: Thiohalophilus thiocyanatoxydans corrig.
Sorokin et al. 2007a, VL117.@en

Thi.o.ha.lo.spi’ra. Gr. neut. n. thion sulfur; Gr. masc. n. hals, halos salt of the sea; L. fem. n. spira spiral; N.L. fem. n. Thiohalospira salt-loving sulfur spiral. The genus Thiohalospira was originally classified as a member of the family Ectothiorhodospiraceae, order Chromatiales, within the Gammaproteobacteria. It includes obligately aerobic, moderately to extremely halophilic, neutrophilic, or facultatively alkaliphilic chemolithoautotrophic sulfur-oxidizing bacteria. CO2 is assimilated via the Calvin–Benson–Bassham cycle. The genus includes two species: the type species Thiohalospira halophila, which is extremely halophilic and neutrophilic, and the moderately halophilic and facultatively alkaliphilic Thiohalospira alkaliphila. DNA G+C content (mol%) 65.6 (T. alkaliphila, Tm)–69.1 (T. halophila, genome). Type species: Thiohalospira halophila Sorokin et al. 2008aVP.@en

De.sul.fu.ri.ba.cil’lus L. pref. de-, from; L. neut. n. sulfur, sulfur; N.L. masc. n. bacillus, a rod; N.L. masc. n. Desulfuribacillus, a sulfur-reducing rod. The genus Desulfuribacillus was originally described
as a deep unaffiliated lineage in the order Bacillales. However, according to more recent phylogenomic analyses, it can be assigned into a separate class-level taxon. It includes obligately anaerobic, Gram-positive, spore-forming bacteria capable of anaerobic respiration of thiosulfate, sulfur, dimethyl sulfoxide (DMSO), arsenate, antimonate, nitrate, nitrite, selenate, and selenite. Members are low to moderately salt-tolerant and alkaliphilic. They inhabit anaerobic sediments
of soda lakes. The genus currently includes the type species Desulfuribacillus alkaliarsenatis and Desulfuribacillus stibiiarsenatis. DNA G+C content (mol%): 37.5–38.2 (genomic). Type species: Desulfuribacillus alkaliarsenatis Sorokin et al. 2014, VL159.@en

De.sul.fu.ri.ba.cil.la’les. N.L. masc. n. Desulfuribacillales, the order of the genus Desulfuribacillus.
Order Desulfuribacillales is the only order of the class Desulfuribacillia, which forms a deep-branching phylogenetic lineage at the base of the phylum Firmicutes. It consists of a single-family Desulfuribacillaceae and a genus Desulfuribacillus, whose species are haloalkaliphilic anaerobes with a respiratory metabolism. DNA G +C content (mol%): 37.5–38.2 (genome). Type genus: Desulfuribacillus Sorokin et al. 2014, VL160.@en

Thi.o.halo.bac’ter. Gr. neut. n. thion sulfur; Gr. masc. n. hals, halos salt of the sea; N.L. masc. n. bacter a rod; N.L. masc. n. Thiohalobacter halophilic sulfur rod.
The genus Thiohalobacter was originally classified as an unaffiliated member of a deep-lineage of the Gammaproteobacteria. It is a moderately halophilic, neutrophilic and obligately aerobic, chemolithoautotrophic sulfur-oxidizing bacterium with the ability to utilize thiocyanate as the electron donor. CO2 is assimilated via the Calvin–Benson–Bassham cycle. The genus includes a single species T. thiocyanaticus, which is the type species. DNA G+C content (mol%): 64.2 (genome). Type species: Thiohalobacter thiocyanaticus Sorokin et al. 2010VP@en

Thi.o.halo.mo’nas Gr. neut. n. thion sulfur; Gr. masc. n. hals, halos salt of the sea; Gr. fem. n. monas unit, monad; N.L. fem. n. Thiohalomonas halophilic sulfur-utilizing monad.
The genus Thiohalomonas was originally classified as a member of an unaffiliated deep lineage of the Gammaproteobacteria. It includes moderately halophilic and neutrophilic chemolithoautotrophs utilizing reduced sulfur compounds as the energy sources/electron donors and O2 and nitrate as the electron acceptors. CO2 is assimilated via the Calvin–Benson–Bassham cycle. The genus currently
includes two species, Thiohalomonas denitrificans, which is the type species, and Thiohalomonas nitratireducens. The habitat is hypersaline lakes with neutral pH.
DNA G+C content (mol%): 58–60 (Tm and genome of the type strain).
Type species: Thiohalomonas denitrificans Sorokin et al. 2007aVP.@en

Thi.o.ha.lo.rhab’dus. Gr. neut. n. thion sulfur; Gr. masc. n. hals, halos salt of the sea; Gr. fem. n. rhabdos rod, stick; N.L. fem. n. Thiohalorhabdus halophilic sulfur rod.
The genus Thiohalorhabdus was originally classified as a deep unaffiliated lineage within the Gammaproteobacteria. It is an extremely halophilic, neutrophilic
chemolithoautotroph using reduced sulfur compounds as the energy source and electron donor and O2 or nitrate as the electron acceptor. CO2 is assimilated
via the Calvin–Benson–Bassham cycle. The genus includes a single species Thiohalorhabdus denitrificans, which is the type species. Habitat—hypersaline
lakes and solar salterns. DNA G +C content (mol%): 68.9 (genome of type strain). Type species: Thiohalorhabdus denitrificans Sorokin et al. 2008aVP@en

N.L. masc. n. Desulfuribacillaceae, the family of the genus Desulfuribacillus.
The family Desulfuribacillaceae incorporates obligately anaerobic, low-to moderately salt-tolerant, and alkaliphilic bacteria with respiratory metabolism inhabiting soda lakes. They utilize a limited number of electron donors, including H2, formate, pyruvate, and lactate and a variety of electron acceptors, including sulfur compounds (sulfur, thiosulfate, DMSO) and several oxyanions, including arsenate, selenite, selenite, antimonate, nitrate, and nitrite. Pyruvate can also be fermented. The family consists of a single genus Desulfuribacillus, which includes the type species Desulfuribacillus alkaliarsenatis and Desulfuribacillus
stibiiarsenatis. DNA G +C content (mol%): 37.5–38.2 (genome). Type genus: Desulfuribacillus Sorokin et al. 2014, VL159.@en

Thi.o.al.ka.li.bac’ter Gr. neut. n. thion sulfur; M.L. n. alkali (from Arabic al-qalyi, the ashes of saltwort) sodaash; N.L. masc. n. bacter a rod; N.L. masc. n. Thioalkalibacter rod-shaped bacterium that loves alkaline conditions and utilizes sulfur compounds. The genus Thioalkalibacter was originally classified as a member of the cluster Halothiobacillus
halophilus-Htb. hydrothermalis, but later, it was placed into a separate family Thioalkalibacteraceae together with the genus Guyparkeria (accommodating former Halothiobacillus species Htb. halophila and Htb. hydrothermalis) in the Gammaproteobacteria. Thioalkalibacter is a moderately halophilic and facultatively alkaliphilic
chemolithoautotrophic sulfur-oxidizing bacterium utilizing reduced sulfur compounds as energy source and O2 as an electron acceptor. CO2 is assimilated via the Calvin–Benson–Bassham cycle. The genus includes a single species Thioalkalibacter halophilus, which is the type species. Habitat is hypersaline alkaline lakes. DNA G + C content (mol%): 54.2 (genome). Type species: Thioalkalibacter halophilus Banciu et al.2009, VL 127.@en

Me.tha.no.na.tron.ar.chae’um N.L. neut. n. methanum methane; N.L. pref. methano- pertaining to methane; N.L. n. natron, arbitrarily derived from the Arabic n. natrun natron, soda; N.L. neut. n. archaeum pertaining
to archaios, -e, -on ancient; N.L. neut. n. Methanonatronarchaeum a soda-loving archaeon forming methane. The genus Methanonatronarchaeum includes obligately
anaerobic, extremely haloalkaliphilic, and moderately thermophilic methanogens with small coccoid cells of 0.4–0.5 μm producing methane by reduction of C1-methylated compounds using either H2 or formate as external electron donors. Yeast extract or acetate is required as C-source. Cells accumulate intracellular potassium as a compatible solute. Core membrane lipids are dominated by archaeol (diphytanyl glycerol ether, DGE) and glycerol diphytanyl glycerol tetraether (GDGT-0). The habitat is hypersaline
soda lakes. The genus consists of a single species M. thermophilum, which is the type species. A member of the class Methanonatronarchaeia within a newly proposed
phylum Halobacteriota (formerly part of Euryarchaeota). DNA G+C content (mol%): 37.9 (genome of the type strain). Type species: Methanonatronarchaeum thermophilum
Sorokin, Merkel, Abbas, Makarova, Rijpstra, et al. 2018, 2206VP.
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De.sul.fu.ri.spi’ra. L. pref. de from, off, away; L. neut. n. sulfur sulfur; L. fem. n. spira, spiral; L. fem. n. Desulfurispira, a spirillum that reduces sulfur. The genus Desulfurispira is classified as a member of the family Chrysiogenaceae in the phylum Chrysiogenetes (Sorokin and Muyzer, 2010a, 2010b). Members of the Desulfurispira are obligate anaerobes which can use sulfur or arsenate as electron acceptors. They are moderately salt tolerant and obligately alkaliphilic mesophiles. The genus currently includes a single species, Desulfurispira natronophila, including the type strain AHT11T and a second strain AHT19 (Sorokin and Muyzer, 2010a). DNA G+C content (mol%): 49.2–51.8 (Tm). Type species: Desulfurispiria natronophila Sorokin and Muyzer 2010b, 2509VP (Effectively published: Sorokin and Muyzer, 2010a, 354).@en

De.sul.fu.ri.spi.ril’lum. L. pref. de from, off, away; L. neut. n. sulfur sulfur; N.L. dim. neut. n. spirillum, a small spiral (from L. fem. n. spira, spiral); N.L. neut. n. Desulfurispirillum, a spirillum that reduces sulfur. The genus Desulfurispirillum is a member of the family Chrysiogenaceae in the phylum Chrysiogenetes. Members of Desulfurispirillum are obligate anaerobes, which can reduce nitrate to ammonia. Some strains also respire arsenate, sulfur, or selenate. They are moderately salt tolerant and either alkaliphilic or neutrophilic mesophiles. The genus currently includes two species: D. alkaliphilum, the type species of the genus, and D. indicum. DNA G+C content (mol%): 45–56. Type species: Desulfurispirillum alkaliphilum Sorokin, Foti, Tindall and Muyzer 2010, 1VP (Effective publication: Sorokin, Foti, Tindall and Muyzer 2007, 368).@en

[De.thi.o.bac’ter L. pref. de from, off, away; Gr. neut. n. theion sulfur; N.L. masc. n. bacter a rod; N.L. masc. n. Dethiobacter rod-shaped bacterium that reduces sulfur
compounds]. Dethiobacter is a moderately salt-tolerant and obligately alkaliphilic sulfidogenic anaerobe isolated from soda lake sediments. The genus forms a deep lineage
in the Firmicutes, which is currently classified within the class Dethiobacteria. It is obligately haloalkaliphilic, facultatively chemolithoautotrophic, anaerobic bacterium
able to grow by sulfur and thiosulfate respiration and sulfur disproportionation. The genus includes a single species D. alkaliphilus, which is the type species. DNA G+C content (mol%): 48.5 (genome).Type species: Dethiobacter alkaliphilus Sorokin,Tourova, Mussman and Muyzer, 2008b, 1993VP (Effective publication: Sorokin, Tourova, Mussman and
Muyzer, 2008a, 438).@en

Me.tha.no.na.tron.ar.chae.a.ce’ae. N.L. neut. n. Methanonatronarchaeum,
the type genus of the family; -aceae ending to denote a family; N.L. fem. pl. n. Methanonatronarchaeaceae, the Methanonatronarchaeum family. The family Methanonatronarchaeaceae includes obligately anaerobic, extremely halophilic, or haloalkaliphilic methanogens with small coccoid cells which produce methane by reduction of C1-methylated compounds with either H2 or formate and assimilate either amino acids or acetate as C source. Cells accumulate intracellular potassium as a compatible solute. It is found exclusively in hypersaline lakes. The family consists of two genera: alkaliphilic Methanonatronarchaeum, which is the type genus, and neutrophilic Candidatus
Methanohalarchaeum. DNA G+C content (mol%): 35.4–38.0 (genomes).
Type genus: Methanonatronarchaeum Sorokin, Merkel, Abbas, Makarova, Rijpstra, Koenen et al. 2018, 2205VP.@en

Me.tha.no.hal’ar.chae.um N.L. neut. n. methanum methane; N.L. pref. methano- pertaining to methane; Gr. masc. n. hals, halos salt; N.L. neut. n. archaeum
(pertaining to archaios, -e, -on) ancient; N.L. neut. n. Methanohalarchaeum a salt-loving archaeon forming methane. The candidate genus Ca. Methanohalarchaeum includes obligately anaerobic, extremely halophilic,
neutrophilic, and moderately thermophilic methanogens with small coccoid cells producing methane by reduction of C1-methylated compounds using either
H2 or formate as electron donors. Amino acids or acetate is required as C-source for assimilation. Core membrane lipids are represented by diphytanyl glycerol
tetra- and diethers. Cells accumulate potassium as a compatible solute. They inhabit hypersaline lakes or salterns with neutral pH. The genus contains a single
candidate species Ca. M. thermophilum, which is the type species. It is amember of the class Methanonatronarchaeia within a newly proposed phylum Halobacteriota (formerly part of the phylum Euryarchaeota). DNA G+C content (mol%): 35.4 (genome of the type strain).@en

Me.tha.no.na.tron.ar.chae.a’les N.L. neut. n. Methanonatronarchaeum the type genus of the order; -ales ending to denote an order; N.L. fem. pl. n. Methanonatronarchaeales the Methanonatronarchaeum order. Type genus: Methanonatronarchaeum Sorokin, Merkel, Abbas, Makarova, Rijpstra, Koenen et al.
2018, 2205VP.@en

Me.tha.no.na.tron.ar.chae’i.a. N.L. fem. pl. n. Methanonatronarchaeales, the type order of the class; -ia ending to denote a class; N.L. neut. pl. n. Methanonatronarchaeaia, the Methanonatronarchaeales class. Type order: Methanonatronarchaeales Sorokin, Merkel, Abbas, Makarova, Rijpstra, Koenen, et al.
2018, 2206VP.@en

Me.tha.no.sal’ sum. N.L. pref. methano pertaining to methane; L. neut. part. adj. salsum salted, salty; N.L.neut. n. Methanosalsum the salty methane-producing organism.
The genus Methanosalsum, classified within the family Methanosarcinaceae, order Methanosarcinales, consists of obligately anaerobic high salt-tolerant and alkaliphilic euryarchaea that grow by methanogenic fermentation of C1-methylated compounds. It inhabits inland, hypersaline alkaline lakes. The genus includes two species, Methanosalsum zhilinae, which is the type species of the genus, and Methanosalsum natronophilum. DNA G+C content (mol%): 38–44.8 (Tm). Type species: Methanosalsum zhilinae (Mathrani,
Boone, Mah, Fox and Lau 1988) Boone and Baker, 2002, 686VP (Effectively published: Boone and Baker 2001, 287; Basonym: Methanohalophilus zhilinae Mathrani, Boone, Mah, Fox and Lau 1988, 141).@en