Abstract Ba.cil'lus. N.L. masc. n. Bacillus a rodlet. Bacillota / Bacilli / Caryophanales / Bacillaceae / Bacillus The emended genus Bacillus includes species from two different monophyletic clades, the “Subtilis” and “Cereus” clades. Cells are rod‐shaped, mostly straight, occurring singly, in pairs or chains, and occasionally as long filaments. Endospores usually formed are mostly ellipsoidal in an unswollen sporangium. Mostly Gram‐stain positive, sometimes Gram‐stain variable. A meso ‐diaminopimelate (DAP) direct murein cross‐linkage type is present in the cell wall containing teichoic acids. Cells are motile by peritrichous or (sub)polar flagella, or nonmotile. Aerobes, but many species are facultative anaerobes. The terminal electron acceptor is oxygen with MK‐7 as major respiratory menaquinone, but nitrate respiration is common. Colony morphology and size are variable; some species form pigmented colonies. Mostly mesophilic, with some species/strains showing psychro‐, thermo‐, salt, alkali, or acid tolerance . Catalase is generally produced; several species are oxidase positive. Chemo‐organotrophic. Mostly isolated from soil or soil‐contaminated environments, marine sediments, rhizosphere, plants, but also found in air, water, food, and clinical and animal specimens. The resistance of spores to heat, radiation, disinfectants, and desiccation makes some species persistent contaminants in operating rooms, surgical dressings, pharmaceuticals, and processed foods. Most species are nonpathogenic and rarely cause human or animal infections. Important exceptions are Bacillus anthracis (agent of anthrax), certain Bacillus cereus strains (food poisoning, opportunistic infections), and Bacillus thuringiensis (invertebrate pathogen, bio‐insecticide). The genus also includes agriculturally and industrially important species. The Subtilis and Cereus clades share unique molecular signatures that reliably distinguish them from other Bacillaceae genera. DNA G + C content (mol%) : 34–46 (genome sequences). Type species : Bacillus subtilis Cohn (1872) AL .
Abstract A.e.ri.scar.do'vi.a. Gr. masc. n. aêr (gen. aeros) , air; N.L. fem. n. Scardovia , a bacterial generic name to honor Vittorio Scardovi, an Italian microbiologist; N.L. fem. n. Aeriscardovia , cells similar to the genus Scardovia that can grow in air. Actinomycetota / Actinomycetes / Bifidobacteriales / Bifidobacteriaceae / Aeriscardovia Aeriscardovia consist of Gram‐stain‐positive, catalase‐ and oxidase‐negative, nonmotile, nonspore‐forming cells that form short and irregularly shaped rods. Optimal growth occurs under anaerobic conditions, with aerobic growth yielding elongated cells. 16S rRNA, HSP60, and the genome gene comparisons indicate that Aeriscardovia is phylogenetically located on the periphery of the genus Bifidobacterium belonging to the family Bifidobacteriaceae . To date, only the type species, Aeriscardovia aeriphila , has been described. The genome of A . aeriphila is approximately 1.6 Mb in size. Known habitats are pig caecum, ruminant gastrointestinal tract (goat, yak, dairy cattle), chicken and Grey Crowned Crane guts, and anaerobic bioreactors. DNA G + C content (mol%) : 54.7 (HPLC), 54.0 (Genome). Type species : Aeriscardovia aeriphila Simpson et al. 2004 VP .
Abstract A.ce.ti.cel'la. L. neut. n. acetum , vinegar; L. fem. n. cella , cell; N.L. fem. n. Aceticella , vinegar cell. Bacillota / Thermoanaerobacteria / Thermoanaerobacterales / Thermoanaerobacteraceae / Aceticella The genus Aceticella falls into a monophyletic group of heterotrophic bacteria of the genera Thermoanaerobacterium , Thermoanaerobacter , and Caldanaerobacter within the family Thermoanaerobacteraceae . Cells of the genus Aceticella are Gram‐stain‐positive, spore‐forming, nonmotile rods that occur singly, in pairs, or in chains. Asymmetric cell division leads to the formation of coccoid cells. Stationary growth phase cells are pleomorphic and capable of forming filaments. The genus comprises strictly anaerobic, thermophilic, acidotolerant, obligate chemolithoautotrophic bacteria, growing by acetogenesis with hydrogen, formate, or carbon monoxide as the electron donor and carbon dioxide as the electron acceptor and carbon source. Acetate is the end product of the growth. Sulfide formation is observed in the presence of elemental sulfur or polysulfide, but acetate is also produced. Membrane polar lipids include phospholipids and aminophospholipid. The major cellular fatty acids are iso‐C 15:0 and C 16:0 . Respiratory quinones are absent. Known habitats are terrestrial hot springs, lake sediments, and subsurface waters. DNA G + C content (%) : 33.0 (genome sequence). Type species : Aceticella autotrophica Frolov et al. 2023, VL216.
Abstract Ther. mo. de. sul. fo. bac. te. ri.o'ta. N.L. neut. n. Thermodesulfobacterium , type genus of the phylum; ‐ota , ending to denote a phylum; N.L. pl. neut. n. Thermodesulfobacteriota , the Thermodesulfobacterium phylum.
Abstract Dor.mi.bac.te'ri.a: N.L. masc. n. Dormibacter , a bacterial genus and type genus of the class; ‐ ia ending to denote a class; N.L. neut. pl. n. Dormibacteria , the Dormibacter class. Chloroflexota / Dormibacteria The class Dormibacteria , previously classified as a distinct phylum ( Candidatus Dormibacterota) and candidate division AD3, is the earliest diverging class within the phylum Chloroflexota . Dormibacteria is an as‐yet‐uncultured, globally distributed terrestrial clade that is best known for the genetic capacity of certain of its members to oxidize trace gases (dihydrogen, carbon monoxide) for energy, persistence, and growth via a process termed atmospheric chemosynthesis. Metagenome‐assembled genomes (MAGs) all encode the capacity for aerobic respiration, with certain MAGs additionally encoding the ability for anaerobic respiration. Dormibacteria are ubiquitous in soils, with high relative abundances occurring in cold, arid, and hyperarid deserts of Antarctica. In some members, carbon fixation via the Calvin‐Benson‐Bassham (CBB) cycle is proposed through a “dark” form of RuBisCO, form 1E. Synonyms that have appeared in the literature include Dormibacterota and Dormibacteraeota . Currently, the name Dormibacteria has been validated in the SeqCode Registry. DNA G + C content (mol%) : 66.3–69.2%, an average of 67.9% for nine dereplicated medium to high quality MAGs in NCBI and SeqCode. Type genus : Dormibacter ( ex Ji et al. 2017) Montgomery et al. 2021, Williams et al. 2024.
Abstract Pe.di.o.coc'cus. Gr. neut. n. pedion , a plane surface; N.L. masc. n. coccus , coccus; from Gr. masc. n. kokkos , grain, seed; N.L. masc. n. Pediococcus , coccus growing in one plane Bacillota / “Bacilli” / Lactobacillales / Lactobacillaceae / Pediococcus Bacteria of the genus Pediococcus are Gram‐stain‐positive, nonspore‐forming, facultatively anaerobic, nonmotile, and catalase‐negative cocci that are occasionally ovoid, and either divide and form pairs or divide alternately in two perpendicular directions to form tetrads. Chain formation does not occur. Pediococci have a chemoorganotrophic metabolism and ferment glucose homofermentatively producing lactic acid but no CO 2 . All Pediococcus species produce a mixture of dl ‐lactate from sugar metabolism, except for P. claussenii which produces only the l(+) ‐lactic acid enantiomer. The pediococci are capable of fermenting a range of sugars with different fermentative capacity among the species. Pediococci are widespread in nature and occur in fermented foods including fermented meat, milk and plant products, as well as fermented beverages. Many pediococci produce bacteriocins, of which pediocin PA‐1 is probably the most well‐known. Bacteriocin‐producing strains are used in biotechnological applications for improving food safety. Pediococci also occur in human and animal hosts, particularly in the digestive tract and in human feces. Pediococci generally have small genomes with an average size of 2.02 Mb, encoding an average of 1,907 protein‐coding genes. The genetic diversity observed from genome sequencing is often related to carbohydrate utilizing genes as well as mobile genetic elements, which may encode bacteriocin or bacteriophage genes. As is typical for other lactic acid bacteria, the pediococci have a low mol% GC content of an average of 39% in the DNA. Type species : Pediococcus damnosus Claussen 1903 AL . DNA G + C content (mol%) : 38 (based on genome sequence).
Abstract Cal. di. tri. cho'ta. N.L. fem. n. Caldithrix , type genus of the phylum; ‐ ota , ending to denote a phylum; N.L. pl. neut. n. Calditrichota , the Caldithrix phylum.
Abstract Te.nu.i.fi'lum. L. masc./fem. adj. tenuis , slender, fine, thin; L. neut. n. filum , a thread; N.L. neut. n. Tenuifilum , a slender thread. Bacteroidota / Bacteroidia / Bacteroidales / Tenuifilaceae / Tenuifilum The genus Tenuifilum contains two species with validly published names and belongs to the phylum Bacteroidota , class Bacteroidia, order Bacteroidales, and family Tenuifilaceae . Cells of these species are thin filamentous rods with diderm cell envelope, motile by means of gliding, and are able to form rosettes. These bacteria are strictly anaerobic and neutrophilic thermophiles that grow by fermentation. They reduce elemental sulfur with H 2 S formation. Mono‐, di‐, and polysaccharides as well as proteinaceous substrates serve as carbon and energy sources. Known habitats are shallow marine and terrestrial hot springs, groundwater, host‐associated ecosystems (animal gut and algal surface), and various artificial environments (anaerobic digesters, microbial electrolysis cells, and wastewater). DNA G + C content (%): 38.3–42.1 (genome sequences). Type species : Tenuifilum thalassicum Podosokorskaya et al. 2020, VL197.
Abstract De.fer.ri.vi.bri.o.na'ce.ae. N.L. masc. n. Deferrivibrio type genus of the family; L. fem. pl. n. suff. ‐ aceae , ending to denote a family; N.L. fem. pl. n. Deferrivibrionaceae , the Deferrivibrio family. Chrysiogenota / Deferribacteres / Deferribacterales / Deferrivibrionaceae The Deferrivibrionaceae family belongs to the Deferribacterales order within the Chrysiogenota phylum and accommodates a single genus Deferrivibrio . Only two representatives have been described, Deferrivibrio essentukiensis Es71‐Z0220 T and Deferrivibrio metallireducens V6Fe1 T , which are genetically, but not phenotypically, very similar. The family Deferrivibrionaceae includes anaerobic chemoorgano‐ or chemolithotrophic bacteria that inhabit aquifers, hot vents of marine sediments, and petroleum reservoirs. They are moderate thermophiles, neutrophiles, and halotolerant microorganisms that use organic acids, peptides, or molecular hydrogen as energy sources, and Fe(III) compounds in insoluble form, Mn(IV), nitrate, or elemental sulfur as electron acceptors. Some members of this family ferment organic acids and peptides and perform autotrophic carbon fixation, probably via the reversed oxidative TCA cycle. DNA G + C content (%) : 34.04–34.8 (genome sequence). Type genus : Deferrivibrio Zavarzina et al. 2022, VL211.
Abstract Pseu. do. mo. na. do'ta. N.L. fem. n. Pseudomonas , type genus of the phylum; ‐ota , ending to denote a phylum; N.L. pl. neut. n. Pseudomonadota , the Pseudomonas phylum.
Abstract Lac.to.ba.cil'lus. L. neut. n. lac (gen. lactis ), milk; L. masc. n. bacillus , a small rod; N.L. masc. n. Lactobacillus , milk rodlet. Bacillota / “Bacilli” / Lactobacillales / Lactobacillaceae / Lactobacillus After reclassification of the lactobacilli, the genus Lactobacillus comprises 52 species of Gram‐stain‐positive, rod‐shaped, thermophilic, homofermentative bacteria with validly published names. Two of these species have been shown to be later synonyms, three others are today considered subspecies, and thus there are 47 species‐level taxa. Most strains grow up to 40–45°C, some up to 55°C. In comparison to other lactobacilli genera, strains of Lactobacillus are therefore referred to as thermophilic. Lactobacillus is adapted to a host associated lifestyle. Congruently, strains have small to medium sized genomes ranging from 1.27 to 2.33 Mb. The L. melliventris clade is found in bees in the family Apidae ; most of them are isolated from Apis mellifera, the honey bee. Most other species inhabit the intestine, oral cavity and reproductive tract of vertebrate hosts. The habitats of Lactobacillus species are often shared with heterofermentative lactobacilli. Lactobacillus species are of importance in many fermentation processes occurring during the production and preservation of food and feed, especially fermented dairy and plant products, but can also be associated with spoilage. The fermentation type is homolactic and many species ferment a variety of carbohydrates. Species that have adapted to specific narrow niches, such as the bee intestine, human vagina and dairy fermentations, utilize only a very reduced spectrum of carbohydrates. DNA G + C content (mol%) : 32.5–52.1 (genome). Type species : Lactobacillus delbrueckii Beijerinck 1901 AL (basonym: “Bacillus delbruecki” Leichmann 1896).
Abstract U.re.a.plas'ma. Chem. fem. n. urea , urea; Gr. neut. n. plasma , anything formed or moulded, image, figure, form; N.L. neut. n. Ureaplasma , urea form [probably better: Ureiplasma]. Mycoplasmatota / Mollicutes / Mycoplasmatales / Mycoplasmataceae / Ureaplasma Bacteria belonging to the genus Ureaplasma are small (100–800 nm in diameter), pleomorphic, lack a peptidoglycan cell wall, and are surrounded by a phospholipid bilayer membrane. Primarily coccoid in appearance, although coccobacillary and filamentous forms can also occur. These bacteria form exceptionally small ( < 0.2 mm) colonies on solid media. Similar to the closely related genus Mycoplasma , ureaplasmas have small (0.75–1.01 Mb) A+T‐rich genomes, use the codon UGA to encode tryptophan, and are nutritionally fastidious, requiring exogenous sterols, polyamines, and peptides for axenic growth. Unlike mycoplasmas, ureaplasmas are incredibly unique as they hydrolyze urea for ATP synthesis instead of glucose or arginine. All species are commensals or opportunistic parasites of their vertebrate hosts. DNA G + C content (mol%) : 25.4–36.8 (complete genome sequences). Type species : Ureaplasma urealyticum Shepard et al. 1974 AL emend. Robertson et al. 2002.
Abstract Ig. na. vi. bac. te. ri.o'ta. N.L. neut. n. Ignavibacterium , type genus of the phylum; ‐ ota , ending to denote a phylum; N.L.pl. neut. n. Ignavibacteriota , the Ignavibacterium phylum. The description of the phylum Ignavibacteriota is mainly defined based on the phylogenetic position of the 16S rRNA gene, 23 rRNA gene, and RecA protein sequences. The description is the same as that for the order Ignavibacteriales . Type genus : Ignavibacterium Iino et al. 2010 VP .
Abstract Win.mi.spi.ra'ce.ae. N.L. fem. n. Winmispira , type genus of the family; L. fem. pl. n. suff. ‐aceae , ending to denote a family; N.L. fem. pl. n. Winmispiraceae , the Winmispira family. Spirochaetota / Spirochaetia / Winmispirales / Winmispiraceae The family Winmispiraceae contains only two described genera, that is, Winmispira and Rarispira . It forms one of the two family‐level lineages within the order Winmispirales being most closely related to the family‐level lineage DTKZ01, which is designated in GTDB 10‐RS226 database and accommodates only metagenome‐assembled genomes (MAGs). Representatives of the family are strictly anaerobic, thermophilic, neutrophilic chemoorganoheterotrophic bacteria with an ability to utilize a wide spectrum of carbohydrates, including polysaccharides. These bacteria grow by fermentation, and Rarispira pelagica also reduces sulfur and thiosulfate to hydrogen sulfide. The two cultured representatives, Winmispira thermophila Z‐1203 T and R. pelagica 38H‐sp T , are found in marine hot springs. DNA G + C content (%) : 40.1–60.9 (genome sequences). Type genus : Winmispira Podosokorskaya et al. 2025, VL224.
Abstract Spi. ro. chae. to'ta. N.L. fem. n. Spirochaeta , type genus of the phylum; ‐ ota , ending to denote a phylum; N.L. pl. neut. n. Spirochaetota , the Spirochaeta phylum.
Abstract Lac.to.ba.cil.la'ce.ae. N.L. masc. n. Lactobacillus , type genus of the family; L. fem. pl. n. suff. ‐aceae , ending to denote a family; N.L. fem. pl. n. Lactobacillaceae , the Lactobacillus family. Bacillota / “Bacilli” / Lactobacillales / Lactobacillaceae The emended family Lactobacillaceae was proposed based on phylogenomic analyses and encompassed all genera previously included in the families Lactobacillaceae Winslow et al. 1917 AL and Leuconostocaceae Schleifer 2010, VL132. This family currently comprises >420 non‐synonymous species classified into 36 genera and one Candidatus genus (July 2025). Cells are Gram‐stain‐positive, nonspore‐forming, facultatively or strictly anaerobic bacteria. Cells are coccoid or rod‐shaped may form chains, pairs, or in the case of Pediococcus, tetrads. The main product of the fermentative metabolism is lactate, and other products may be acetate, ethanol, CO 2 , formate, or succinate. Members of the Lactobacillaceae family have complex nutritional requirements for amino acids, peptides, nucleic acid derivatives, vitamins, salts, fatty acids or fatty acid esters, and fermentable carbohydrates. Lactobacillaceae is the only family in the order Lactobacillales that includes homofermentative and heterofermentative microorganisms. DNA G + C content (mol%) : 30–62 (genome sequences). Type genus : Lactobacillus Beijerinck 1901 AL emend. Haakensen et al. 2009, Cai et al. 2012, Zheng et al. 2020.
Abstract Therm.a.tri.bac'ter. Gr. masc. adj. thermos , hot; N.L. masc. n. Atribacter , a bacterial genus; N.L. masc. n. Thermatribacter , a thermophilic Atribacter . Atribacterota / Atribacteria / Atribacterales / Thermatribacteraceae / Thermatribacter Members of the genus Thermatribacter are anaerobic, thermophilic, fermentative bacteria. Their defining cellular feature is a three‐layered cell wall comprising cytoplasmic and outer membranes, as well as a distinct intracytoplasmic membrane that encloses genomic DNA. They are saccharolytic, with some strains capable of hydrolyzing polysaccharides like xylan and gellan. Known habitats are oil reservoirs, gas fields, hot springs, anaerobic reactors, and soil. Genome sizes of isolated cultures are in the range 2.2–2.3 Mb, with a DNA G + C content of 44.82–45.95 mol%. Thermatribacter members universally possess hydrogenases and Rnf complexes that support an energy‐producing lifestyle through glycolysis. Phylogenetic analyses assign Atrimonas thermophila M15 to Thermatribacter velox . DNA G + C content (mol%) : 45.88 (WGS). Type species : Thermatribacter velox Jiao et al. 2024, VL220.
Abstract An.a.e.ro.ba'ca. Gr. pref. an‐ , not (here: inseparable prefix); Gr. masc. n. aêr , air (gen. aeros); L. fem. n. baca , berry; N.L. fem. n. Anaerobaca , a berry, not living in air. Planctomycetota / Phycisphaerae / Sedimentisphaerales / Anaerobacaceae / Anaerobaca The genus Anaerobaca contains one species with a validly published name and belongs to the phylum Planctomycetota, class Phycisphaerae, order Sedimentisphaerales , and family Anaerobacaceae . Cells of this species are small cocci with Gram‐negative type of cell wall, dividing by binary fission. Strict anaerobes. Dependent on the presence of Na + ions in the cultivation medium. These mesophilic alkalitolerant bacteria have a chemoorganotrophic lifestyle and have a strict fermentative type of metabolism, degrading simple and complex carbohydrates, but not proteinaceous substrates. Known habitats are various anaerobic organic‐rich habitats such as anaerobic bioreactors, marine suboxic sediments, and landfill leachate sediment. DNA G + C content (mol%) : 62.48 (genome analysis). Type species : Anaerobaca lacustris Khomyakova et al. 2024, VL220.
Abstract Ver. ru. co. mi. cro. bi.o'ta. N.L. neut. n. Verrucomicrobium , type genus of the phylum; ‐ ota , ending to denote a phylum; N.L. pl. neut. n. Verrucomicrobiota , the Verrucomicrobium phylum.
Abstract Ra.ri.spi'ra. L. masc. adj. rarus , rare; Gr. fem. n. speîra , coil, spire; N.L. fem. n. Rarispira , a rare spiral bacterium. Spirochaetota / Spirochaetia / Winmispirales / Winmispiraceae / Rarispira The genus Rarispira contains one species with a validly published name and belongs to the phylum Spirochaetota , class Spirochaetia, order Winmispirales, family Winmispiraceae . Cells of this species are thin helices with regular coiling and diderm cell envelope, motile by periplasmic flagella. These bacteria are strictly anaerobic, neutrophilic moderate thermophiles, that grow by fermentation. Reduce sulfur and thiosulfate to hydrogen sulfide. Mono‐, di‐, and polysaccharides serve as carbon and energy sources. Known habitats are shallow marine hydrothermal vents. DNA G + C content (%) : 40.1 (genome sequence). Type species : Rarispira pelagica Podosokorskaya et al. 2025, VL224.
