Enterobacterales is an order of

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 ...

, non-spore forming, facultatively anaerobic, rod-shaped bacteria with the class

Gammaproteobacteria Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota (synonym Proteobacteria). It contains about 250 genera, which makes it the most genera-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically imp ...

. The

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...

of this order is ''

Enterobacter ''Enterobacter'' is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae. It is the type genus of the order Enterobacterales. Several strains of these bacteria are ...

.'' The name Enterobacterales is derived from the Latin term ''Enterobacter'', referring the type genus of the order and the suffix "-ales", an ending used to denote an order. Together, Enterobacterales refers to an order whose nomenclatural type is the genus ''Enterobacter''.

Historical Identification and Systematics

Enterobacterales was proposed in 2005 under the name "Enterobacteriales". However, the name "Enterobacteriales" was not validated according to the rules of the ''

International Code of Nomenclature of Prokaryotes The International Code of Nomenclature of Prokaryotes (ICNP) formerly the International Code of Nomenclature of Bacteria (ICNB) or Bacteriological Code (BC) governs the scientific names for Bacteria and Archaea.P. H. A. Sneath, 2003. A short his ...

,'' thus it lacked standing in nomenclature, so the name was written in parentheses. "Enterobacteriales" was a

monotypic order In biology, a monotypic taxon is a taxonomic group ( taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

, containing only the family ''

Enterobacteriaceae Enterobacteriaceae is a large family of Gram-negative bacteria. It was first proposed by Rahn in 1936, and now includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject of debate, but o ...

'', and shared its type genus ''Escherichia''.NCB
Enterobacterales
accessed 9 Mar 2013 The order contained a large, diverse group of species, occupying distinct ecological niches and possessing a variety of biochemical characteristics. Many genera within the order have significant impacts on human activity, such as the pathogenic species ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...

Salmonella enterica ''Salmonella enterica'' (formerly ''Salmonella choleraesuis'') is a rod-headed, flagellate, facultative anaerobic, Gram-negative bacterium and a species of the genus ''Salmonella''. A number of its serovars are serious human pathogens. Epidemi ...

,'' and ''

Yersinia pestis ''Yersinia pestis'' (''Y. pestis''; formerly '' Pasteurella pestis'') is a gram-negative, non-motile, coccobacillus bacterium without spores that is related to both ''Yersinia pseudotuberculosis'' and ''Yersinia enterocolitica''. It is a facult ...

'', as well as agriculture-harming phytopathogens such as members of the genera '' Dickeya,

Pectobacterium ''Pectobacterium'' is a bacterial genus of the family Pectobacteriaceae; it used to be a member of the genus '' Erwinia'', which was split into three genera: ''Erwinia'', ''Pectobacterium'', and ''Brenneria''. Species include ''Pectobacterium ...

Brenneria ''Brenneria'' is a genus of Pectobacteriaceae, containing mostly pathogens of woody plants. This genus is named after the microbiologist Don J. Brenner. Some members of this genus were formerly placed in ''Erwinia''. Species Species now pl ...

Erwinia ''Erwinia'' is a genus of Enterobacterales bacteria containing mostly plant pathogenic species which was named for the famous plant pathologist, Erwin Frink Smith. It contains Gram-negative bacteria related to ''Escherichia coli'', ''Shigella'', ...

'' and ''

Pantoea ''Pantoea'' is a genus of Gram-negative bacteria of the family Erwiniaceae, recently separated from the genus ''Enterobacter''. This genus includes at least 20 species. ''Pantoea'' bacteria are yellow pigmented, ferment lactose, are motile, and ...

''. The large number of species as well as the range of different biochemical characteristics made describing the order and its subgroups extremely difficult. The assignment and classification of this order was largely based on 16S rRNA genome sequences, which is known to have low discriminatory power and yield different results depending on the algorithm and organism strain used. In addition, these analyses have shown that 'Enterobacteriales' exhibited polyphyletic branching, with distinct subgroups. In 2016, "Enterobacteriales" was proposed to be reclassified as Enterobacterales, and the type genus changed to ''Enterobacter'' in accordance with the ''International Code of Nomenclature of Prokaryotes.'' In addition, several new families within the order Enterobacterales were proposed, consisting of species that were formerly members of the family ''

'' based on groupings found in phylogenetic trees constructed based on conserved genomes, 16S rRNA sequences and multi-locus sequence analysis as well as independent molecular markers (

conserved signature indels Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...

). As of 2021, the order Enterobacterales contains 7 validly published families (''

Budviciaceae The ''Budviciaceae'' are a family of Gram-negative bacteria. This family is a member of the order Enterobacterales in the class Gammaproteobacteria of the phylum Pseudomonadota. The type genus of this family is '' Budvicia.'' The name ''Budvi ...

Erwiniaceae The ''Erwiniaceae'' are a family of Gram-negative bacteria which includes a number of plant pathogens and insect endosymbionts. This family is a member of the order Enterobacterales in the class Gammaproteobacteria of the phylum Pseudomonadot ...

Hafniaceae The ''Hafniaceae'' are a family of Gram-negative bacteria. This family is a member of the order Enterobacterales in the class Gammaproteobacteria of the phylum Pseudomonadota. Genera in this family include the type genus '' Hafnia'', along wit ...

Morganellaceae The Morganellaceae are a family of Gram-negative bacteria that include some important human pathogens formerly classified as Enterobacteriaceae. This family is a member of the order Enterobacterales in the class Gammaproteobacteria of the phylu ...

, Pectobacteriaceae'' and ''

Yersiniaceae The Yersiniaceae are a family of Gram-negative bacteria that includes some familiar pathogens. For example, the type genus ''Yersinia'' includes ''Yersinia pestis'', the causative agent of plague. This family is a member of the order Enterobacter ...

'').

Molecular Signatures

Analyses of genome sequences from Enterobacterales species identified five

(CSIs) for this order in the proteins peptide ABC transporter permease, elongation factor P-like protein YeiP,

L-arabinose isomerase In enzymology, a L-arabinose isomerase () is an enzyme that catalyzes the chemical reaction :L-arabinose \rightleftharpoons L-ribulose Hence, this enzyme has one substrate, L-arabinose, and one product, L-ribulose. This enzyme belongs to the ...

pyrophosphatase Pyrophosphatases, also known as diphosphatases, are acid anhydride hydrolases that act upon diphosphate bonds. Examples include: * Inorganic pyrophosphatase Inorganic pyrophosphatase (or inorganic diphosphatase, PPase) is an enzyme () tha ...

, and a hypothetical protein, which in most cases are exclusively shared by either all or most members of this order. These CSIs provide a molecular means of demarcating this order from other Gammaproteobacteria and supports the monophyletic nature of the order Enterobacterales.

Genera

Validly published genera

The following genera have been validly published, thus they have "Standing in Nomenclature". The year the genus was proposed is listed in parentheses after the genus name. *''

Arsenophonus ''Arsenophonus'' is a genus of Morganellaceae, of the Gammaproteobacteria. Members of the ''Arsenophonus'' genus are increasingly discovered bacterial symbionts of arthropods that are estimated to infect over 5% of arthropod species globally a ...

'' (1991) *''

Biostraticola ''Biostraticola'' is a Gram-negative, rod-shaped, non-endospore-forming, facultatively anaerobic and motile genus of bacteria within the family of Pectobacteriaceae The ''Pectobacteriaceae'' are a family of Gram-negative bacteria which largely ...

'' (2008) *''

'' (1999) *'' Buchnera'' (1991) *'' Budvicia'' (1985) *'' Buttiauxella'' (1982) *''

Cedecea ''Cedecea'' is a genus of extremely rare bacteria of the family Enterobacteriaceae. The name of this genus was derived from CDC, the abbreviation for the Centers for Disease Control where the initial members of this genus were discovered. This ...

'' (1981) *''

Chania Chania ( el, Χανιά ; vec, La Canea), also spelled Hania, is a city in Greece and the capital of the Chania regional unit. It lies along the north west coast of the island Crete, about west of Rethymno and west of Heraklion. The muni ...

'' (2016) *''

Citrobacter ''Citrobacter'' is a genus of Gram-negative coliform bacteria in the family Enterobacteriaceae. The species ''C. amalonaticus'', ''C. koseri'', and ''C. freundii'' can use citrate as a sole carbon source. ''Citrobacter'' species are different ...

'' (1932) *'' Cosenzaea'' (2011) *'' Cronobacter'' (2008) *'' Dickeya'' (2005) *'' Edwardsiella'' (1965) *'' Enterobacillus'' (2015) *''

'' (1960) *''

'' (1920) *''

Escherichia ''Escherichia'' () is a genus of Gram-negative, non- spore-forming, facultatively anaerobic, rod-shaped bacteria from the family Enterobacteriaceae. In those species which are inhabitants of the gastrointestinal tracts of warm-blooded animals, ...

'' (1919) *''

Ewingella ''Ewingella americana'' is a Gram-negative rod, and the only species in the genus ''Ewingella''. It was first identified and characterized in 1983. ''Ewingella'' is in the family Yersiniaceae. The organism is rarely reported as a human pathoge ...

'' (1984) *'' Franconibacter'' (2014) *'' Gibbsiella'' (2011) *'' Hafnia'' (1954) *'' Izhakiella'' (2016) *''

Klebsiella ''Klebsiella'' is a genus of Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. ''Klebsiella'' species are found everywhere in nature. This is thought to be due to distinct sublineages devel ...

'' (1885) *'' Kluyvera'' (1981) *'' Kosakonia'' (2013) *'' Leclercia'' (1987) *'' Lelliottia'' (2013) *'' Leminorella'' (1985) *'' Limnobaculum'' (2018) *'' Lonsdalea'' (2012) *'' Mangrovibacter'' (2010) *'' Metakosakonia'' (2017) *'' Mixta'' (2018) *'' Moellerella'' (1984) *'' Morganella'' (1943) *'' Obesumbacterium'' (1963) *''

'' (1989) *''

'' (1945) *'' Phaseolibacter'' (2013) *''

Photorhabdus ''Photorhabdus'' is a genus of bioluminescent, gram-negative bacilli which lives symbiotically within entomopathogenic nematodes, hence the name ''photo'' (which means light producing) and ''rhabdus'' (rod shape). ''Photorhabdus'' is known to ...

'' (1993) *''

Phytobacter ''Phytobacter'' is a genus of Gram-negative bacteria emerging from the grouping of isolates previously assigned to various genera of the family Enterobacteriaceae. This genus was first established on the basis of nitrogen fixing isolates fro ...

'' (2017) *'' Plesiomonas'' (1962) *'' Pluralibacter'' (2013) *'' Pragia'' (1988) *''

Proteus In Greek mythology, Proteus (; Ancient Greek: Πρωτεύς, ''Prōteus'') is an early prophetic sea-god or god of rivers and oceanic bodies of water, one of several deities whom Homer calls the "Old Man of the Sea" ''(hálios gérôn)''. ...

'' (1885) *'' Providencia'' (1962) *'' Pseudescherichia'' (2017) *'' Pseudocitrobacter'' (2014) *'' Rahnella'' (1981) *''

Raoultella The genus ''Raoultella'' is composed of Gram-negative, oxidase-negative, aerobic, nonmotile, capsulated, facultatively anaerobic rods (formerly designated ''Klebsiella'') in the family Enterobacteriaceae. It is named after the French bacter ...

'' (2001) *'' Rosenbergiella'' (2013) *''

Rouxiella ''Rouxiella chamberiensis'' is a member of the family Yersiniaceae The Yersiniaceae are a family of Gram-negative bacteria that includes some familiar pathogens. For example, the type genus ''Yersinia'' includes ''Yersinia pestis'', the caus ...

'' (2015) *'' Saccharobacter'' (1990) *''

Salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are '' Salmonella enterica'' and '' Salmonella bongori''. ''S. enterica'' is the type species and is ...

'' (1990) *''

Samsonia ''Samsonia'' is a genus of Gram-negative bacteria in the family Yersiniaceae. Species within this genus were originally found in the bark of diseased ''Erythrina'' trees. Among bacterial plant pathogens within the Enterobacterales, ''Samsonia'' ...

'' (2001) *'' Scandinavium'' (2020) *''

Serratia ''Serratia'' is a genus of Gram-negative, facultatively anaerobic, rod-shaped bacteria of the family Yersiniaceae. According to the List of Prokaryotic names with Standing Nomenclature (LPSN), there are currently 19 species of ''Serratia'' that a ...

'' (1823) *''

Shigella ''Shigella'' is a genus of bacteria that is Gram-negative, facultative anaerobic, non-spore-forming, nonmotile, rod-shaped, and genetically closely related to '' E. coli''. The genus is named after Kiyoshi Shiga, who first discovered it in ...

'' (1919) *'' Shimwellia'' (2010) *'' Siccibacter'' (2014) *'' Sodalis'' (1999) *'' Superficieibacter'' (2018) *'' Tatumella'' (1982) *'' Trabulsiella'' (1992) *'' Wigglesworthia'' (1995) *''

Xenorhabdus ''Xenorhabdus'' is a genus of motile, gram-negative bacteria from the family of the Morganellaceae. All the species of the genus are only known to live in symbiosis with soil entomopathogenic nematodes from the genus '' Steinernema''. Although n ...

'' (1979) *''

Yersinia ''Yersinia'' is a genus of bacteria in the family Yersiniaceae. ''Yersinia'' species are Gram-negative, coccobacilli bacteria, a few micrometers long and fractions of a micrometer in diameter, and are facultative anaerobes. Some members of ''Yer ...

'' (1944) *'' Yokenella'' (1985)

''
Candidatus In prokaryote nomenclature, ''Candidatus'' (Latin for candidate of Roman office) is used to name prokaryotic phyla that are well characterized but yet-uncultured. Contemporary sequencing approaches, such as 16S sequencing or metagenomics, provide m ...
'' genera

Proposed, but have not obtained standing in nomenclature

*''Aquamonas'' (2009) *''Aranicola'' (1997) *''Atlantibacter'' (2016) *''Averyella'' (2005) *''Grimontella'' (2003) *''Guhaiyinggella'' (1995) *''Margalefia'' (2004) *''Tiedjeia'' (2005)

References

Gammaproteobacteria Gram-negative bacteria {{Enterobacterales-stub