Enterobacteriaceae

Enterobacteriaceae

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The Enterobacteriaceae is a large family of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 that includes many of the more familiar pathogen
Pathogenic bacteria
Pathogenic bacteria are bacteria that cause bacterial infection. This article deals with human pathogenic bacteria.Although the vast majority of bacteria are harmless or beneficial, quite a few bacteria are pathogenic...

s, such as Salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...

, Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

, Yersinia pestis
Yersinia pestis
Yersinia pestis is a Gram-negative rod-shaped bacterium. It is a facultative anaerobe that can infect humans and other animals....

, Klebsiella
Klebsiella
Klebsiella is a genus of non-motile, Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. It is named after the German microbiologist Edwin Klebs...

and Shigella
Shigella
Shigella is a genus of Gram-negative, nonspore forming, non-motile, rod-shaped bacteria closely related to Escherichia coli and Salmonella. The causative agent of human shigellosis, Shigella causes disease in primates, but not in other mammals. It is only naturally found in humans and apes. During...

. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria
Gammaproteobacteria
Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae , Vibrionaceae and Pseudomonadaceae. An exceeding number of important pathogens belongs to this class, e.g...

in the phylum Proteobacteria
Proteobacteria
The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....

. Phylogenetically, in the Enterobacteriales, several peptidoglycan
Peptidoglycan
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid...

-less insect endosymbionts form a sister clades to the Enterobacteriaceae, but as they are not validly described
International Code of Nomenclature of Bacteria
The International Code of Nomenclature of Bacteria or Bacteriological Code governs the scientific names for bacteria, including Archaea. It denotes the rules for naming taxa of bacteria, according to their relative rank...

 this group is not officially a taxon; Examples of these species are Sodalis, Buchnera
Buchnera
Buchnera can refer to:*Buchnera , a plant genus from the family Orobanchaceae*Buchnera , a genus of proteobacteria...

, Wiggleworthia,Baumannia and Blochmannia, but not formers rickettsias. Members of the Enterobacteriaceae can be trivially referred to as enterobacteria, as several members live in the intestines of animals. In fact, the etymology of the family is enterobacterium with the suffix to designate a family (aceae) — not after the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Enterobacter
Enterobacter
Enterobacter is a genus of common Gram-negative, facultatively-anaerobic, rod-shaped bacteria of the family Enterobacteriaceae. Several strains of the these bacteria are pathogenic and cause opportunistic infections in immunocompromised hosts and in those who are on mechanical ventilation...

(which would be "Enterobacteraceae")— and the type genus is Escherichia
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, Escherichia species provide a portion of the...

.

Characteristics


Members of the Enterobacteriaceae are rod-shaped
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...

, and are typically 1-5 μm in length. Like other proteobacteria, enterobacteria have Gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 stains, and they are facultative anaerobes, fermenting
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...

 sugars to produce lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

 and various other end products. Most also reduce nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

 to nitrite
Nitrite
The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...

, although exceptions exist (e.g. Photorhabdus). Unlike most similar bacteria, enterobacteria generally lack cytochrome C oxidase
Cytochrome c oxidase
The enzyme cytochrome c oxidase or Complex IV is a large transmembrane protein complex found in bacteria and the mitochondrion.It is the last enzyme in the respiratory electron transport chain of mitochondria located in the mitochondrial membrane...

, although there are exceptions (e.g. Plesiomonas shigelloides
Plesiomonas shigelloides
Plesiomonas shigelloides is a species of bacteria. It is a Gram-negative, rod-shaped bacterium which has been isolated from freshwater, freshwater fish, and shellfish and from many types of animals including cattle, goats, swine, cats, dogs, monkeys, vultures, snakes, and toads.Infections from this...

). Most have many flagella used to move about, but a few genera are non-motile. They are non-spore forming. Catalase reactions vary among Enterobacteriaceae.

Many members of this family are a normal part of the gut flora
Gut flora
Gut flora consists of microorganisms that live in the digestive tracts of animals and is the largest reservoir of human flora. In this context, gut is synonymous with intestinal, and flora with microbiota and microflora....

 found in the intestines of humans and other animals, while others are found in water or soil, or are parasites
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...

 on a variety of different animals and plants. Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

(E. coli) is one of the most important model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...

s, and its genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 and biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

 have been closely studied.

Most members of Enterobacteriaceae have peritrichous Type I fimbriae involved in the adhesion of the bacterial cells to their hosts.
Some enterobacteria produce endotoxin
Endotoxin
Endotoxins are toxins associated with some Gram-negative bacteria. An "endotoxin" is a toxin that is a structural molecule of the bacteria that is recognized by the immune system.-Gram negative:...

s. Endotoxins reside in the cell cytoplasm and released when the cell dies and the cell wall disintegrates. Some members of the Enterobacteriaceae family produce a systemic infection into the blood stream when all the dead bacterial cells release their endotoxins. This is known as endotoxic shock and can lead to instant death.

Identification of Enterobacteriaceae


In order to identify different genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

 of Enterobacteriaceae, a microbiologist may run a series of tests in the lab. These include a range of tubes and agar plates such as the following:
  • Phenol red
    Phenol red
    Phenol red is a pH indicator that is frequently used in cell biology laboratories.-Chemical structure and properties:...

  • Tryptone
    Tryptone
    Tryptone is the assortment of peptides formed by the digestion of casein by the protease trypsin.Tryptone is commonly used in microbiology to produce Lysogeny broth for the growth of E. coli and other microorganisms...

     broth
  • Phenylalanine
    Phenylalanine
    Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...

     agar for detection of production of deaminase, which converts phenylalanine to phenylpyruvic acid.
  • Methyl red
    Methyl red
    Methyl red, also called C.I. Acid Red 2, is an indicator dye that turns red in acidic solutions. It is an azo dye, and is a dark red crystalline powder....

     or Voges-Proskauer test for detection of fermentation of dextrose to glucose. The methyl red tests for acid endproducts. The Voges Proskauer tests for the production of acetylmethylcarbinol.
  • Catalase
    Catalase
    Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen...

     test on nutrient agar
    Nutrient agar
    Nutrient agar is a microbiological growth medium commonly used for the routine cultivation of non-fastidious bacteria. It is useful because it remains solid even at relatively high temperatures. Also, bacteria grown in nutrient agar grows on the surface, and is clearly visible as small colonies...

    . This tests for the production of catalase enzyme, which splits hydrogen peroxide and releases oxygen gas.
  • Oxidase test
    Oxidase test
    The oxidase test is a test used in microbiology to determine if a bacterium produces certain cytochrome c oxidases. It uses disks impregnated with a reagent such as N,N,N′,N′-tetramethyl-p-phenylenediamine or N,N-Dimethyl-p-phenylenediamine , which is also a redox indicator...

     on nutrient agar
    Nutrient agar
    Nutrient agar is a microbiological growth medium commonly used for the routine cultivation of non-fastidious bacteria. It is useful because it remains solid even at relatively high temperatures. Also, bacteria grown in nutrient agar grows on the surface, and is clearly visible as small colonies...

    . This tests for the production of the enzyme oxidase
    Oxidase
    An oxidase is any enzyme that catalyzes an oxidation-reduction reaction involving molecular oxygen as the electron acceptor. In these reactions, oxygen is reduced to water or hydrogen peroxide ....

     which reacts with an aromatic amine to produce a purple color.
  • Nutrient gelatin test to detect activity of the enzyme gelatinase
    Gelatinase
    In biology and chemistry, gelatinase is a proteolytic enzyme that allows a living organism to hydrolyse gelatin into its sub-compounds that can cross the cell membrane and be used by the organism...

    .

Examples/classification


The following non-exhaustive list details bacterial genera classified as members of Enterobacteriaceae.

Genera

  • Alishewanella
    Alishewanella
    Alishewanella is a genus in the phylum Proteobacteria .-Etymology:The name Alishewanella derives from:Latin adjective and pronoun alius, other, another, different; New Latin feminine gender noun Shewanella, a bacterial genus name; New Latin feminine gender noun Alishewanella, the other...

  • Alterococcus
  • Aquamonas
  • Aranicola
  • Arsenophonus
  • Azotivirga
  • Blochmannia
  • Brenneria
    Brenneria
    Brenneria is a genus of Enterobacteria. It is named after the microbiologist Don J. Brenner....

  • Buchnera
    Buchnera (proteobacteria)
    Buchnera aphidicola a member of the Proteobacteria, is the primary endosymbiont of aphids and has been studied in the pea aphid, Acyrthosiphon pisum. It is believed that Buchnera was once a free living gram negative ancestor similar to a modern Enterobacteriaceae such as Escherichia coli...

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

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

  • Cronobacter
    Cronobacter
    Cronobacter is a genus of Gram-negative, facultatively-anaerobic, oxidase negative, catalase positive, rod-shaped bacteria of the family Enterobacteriaceae....

  • Dickeya
    Dickeya
    Dickeyea is a genus of Enterobacteria. It is the result of reclassification of 75 Pectobacterium chrysanthemi strains and Brenneria paradisiaca CFBP 4178 into a new genus named after the American phytopathologist Robert S. Dickey. Several species in this genus, such as Dickeyea dadantii, are...

  • Edwardsiella
    Edwardsiella
    Edwardsiella is a Gram negative, fermentative bacteria of the family Enterobacteriaceae. It was first discovered in snakes in 1962.----Associated persons:Philip R. EdwardsDescription:...

  • Enterobacter
    Enterobacter
    Enterobacter is a genus of common Gram-negative, facultatively-anaerobic, rod-shaped bacteria of the family Enterobacteriaceae. Several strains of the these bacteria are pathogenic and cause opportunistic infections in immunocompromised hosts and in those who are on mechanical ventilation...

  • Erwinia
    Erwinia
    Erwinia is a genus of Enterobacteriaceae bacteria containing mostly plant pathogenic species which was named for the first phytobacteriologist, Erwin Smith. It is a gram negative bacterium related to E. coli, Shigella, Salmonella and Yersinia. It is primarily a rod-shaped bacteria. A well-known...

    , e.g. Erwinia amylovora, Erwinia tracheiphila, Erwinia carotovora
    Erwinia carotovora
    Pectobacterium carotovorum is a bacterium of the family Enterobacteriaceae, which is a plant pathogen with a diverse host range. It causes soft rot and blackleg of potato and vegetables as well as slime flux on many different tree species....

     etc.
  • Escherichia
    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, Escherichia species provide a portion of the...

    , e.g. Escherichia coli
    Escherichia coli
    Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

  • Ewingella
  • Grimontella
  • Hafnia
    Hafnia (bacterium)
    Hafnia is the genus of the Enterobacteriaceae family whose only species is the Gram-negative, facultatively anaerobic, rod-shaped bacterium Hafnia alvei....

  • Klebsiella
    Klebsiella
    Klebsiella is a genus of non-motile, Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. It is named after the German microbiologist Edwin Klebs...

    , e.g. Klebsiella pneumoniae
    Klebsiella pneumoniae
    Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines....

  • Kluyvera
  • Leclercia
  • Leminorella
  • Moellerella
  • Morganella
  • Obesumbacterium
  • Pantoea
    Pantoea
    Pantoea is a genus of Gram-negative bacteria of the family Enterobacteriaceae. It comprises seven species and two sub-species....

  • Pectobacterium see Erwinia
    Erwinia
    Erwinia is a genus of Enterobacteriaceae bacteria containing mostly plant pathogenic species which was named for the first phytobacteriologist, Erwin Smith. It is a gram negative bacterium related to E. coli, Shigella, Salmonella and Yersinia. It is primarily a rod-shaped bacteria. A well-known...

  • Candidatus Phlomobacter
  • Photorhabdus, e.g. Photorhabdus luminescens
    Photorhabdus luminescens
    Photorhabdus luminescens is a Gammaproteobacteria, belonging to the family Enterobacteriaceae, and is a lethal pathogen of insects....

  • Poodoomaamaana
  • Plesiomonas, e.g. Plesiomonas shigelloides
    Plesiomonas shigelloides
    Plesiomonas shigelloides is a species of bacteria. It is a Gram-negative, rod-shaped bacterium which has been isolated from freshwater, freshwater fish, and shellfish and from many types of animals including cattle, goats, swine, cats, dogs, monkeys, vultures, snakes, and toads.Infections from this...

  • Pragia
  • Proteus
    Proteus (bacterium)
    Proteus is a genus of Gram-negative Proteobacteria.-Clinical significance:Three species—P. vulgaris, P. mirabilis, and P. penneri—are opportunistic human pathogens. Proteus includes pathogens responsible for many human urinary tract infections. P. mirabilis causes wound and urinary...

    , e.g. Proteus vulgaris
    Proteus vulgaris
    Proteus vulgaris is a rod-shaped, Gram negative bacterium that inhabits the intestinal tracts of humans and animals. It can be found in soil, water and fecal matter. It is grouped with the enterobacteriaceae and is an opportunistic pathogen of humans...

  • Providencia
    Providencia (bacterium)
    Providencia is a Gram negative, motile bacterium of the family Enterobacteriaceae. Some strains are opportunistic pathogens in humans and can cause urinary tract infections, particularly in patients with long-term indwelling urinary catheters or extensive severe burns. Other strains Providencia...

  • Rahnella
  • Raoultella
    Raoultella
    The genus Raoultella is composed of Gram-negative, oxidase-negative, aerobic, non-motile, capsulated facultatively anaerobic, rods, , in the family Enterobacteriaceae. It is named after the French bacteriologist Didier Raoult...

  • Salmonella
    Salmonella
    Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...

  • Samsonia
  • Serratia
    Serratia
    Serratia is a genus of Gram-negative, facultatively anaerobic, rod-shaped bacteria of the Enterobacteriaceae family. The most common species in the genus, S. marcescens, is normally the only pathogen and usually causes nosocomial infections. However, rare strains of S. plymuthica, S. liquefaciens,...

    , e.g. Serratia marcescens
    Serratia marcescens
    Serratia marcescens is a species of Gram-negative, rod-shaped bacterium in the family Enterobacteriaceae. A human pathogen, S. marcescens is involved in nosocomial infections, particularly catheter-associated bacteremia, urinary tract infections and wound infections, and is responsible for 1.4% of...

  • Shigella
    Shigella
    Shigella is a genus of Gram-negative, nonspore forming, non-motile, rod-shaped bacteria closely related to Escherichia coli and Salmonella. The causative agent of human shigellosis, Shigella causes disease in primates, but not in other mammals. It is only naturally found in humans and apes. During...

  • Sodalis
  • Tatumella
  • Trabulsiella
  • Wigglesworthia
  • Xenorhabdus
    Xenorhabdus
    Xenorhabdus is a genus of bacteria that kills pests, and is released by the nematode Heterorhabditis bacteriophora.-Lifecycle:Xenorhabdus spp. are motile, Gram-negative enterobacteria that form mutualistic associations with entomopathogenic soil nematodes in the genus Steinernema and are ...

  • Yersinia
    Yersinia
    Yersinia is a genus of bacteria in the family Enterobacteriaceae. Yersinia are Gram-negative rod shaped bacteria, a few micrometers long and fractions of a micrometer in diameter, and are facultative anaerobes. Some members of Yersinia are pathogenic in humans; in particular, Y. pestis is the...

    , e.g. Yersinia pestis
    Yersinia pestis
    Yersinia pestis is a Gram-negative rod-shaped bacterium. It is a facultative anaerobe that can infect humans and other animals....

  • Yokenella

External links

  • Enterobacteriaceae genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
  • Evaluation of new computer-enhanced identification program for microorganisms: adaptation of BioBASE for identification of members of the family Enterobacteriaceae http://jcm.asm.org/cgi/content/abstract/34/1/179
  • Brown, A.E. (2009). Benson's microbiological applications: laboratory manual in general microbiology. New york: McGraw- Hill.