Citrobacter

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Citrobacter
Citrobacter freundii (secondary electron micrograph)

Citrobacter freundii
( secondary electron micrograph)

Systematics
Domain : Bacteria (bacteria)
Department : Proteobacteria
Class : Gammaproteobacteria
Order : Enterobacterales
Family : Enterobacteriaceae
Genre : Citrobacter
Scientific name
Citrobacter
Werkman & Gillen 1932

The bacteria of the genus Citrobacter are a group of gram-negative rod bacteria of the enterobacteria family (Enterobacteriaceae). As a rule, they are not pathogenic and occur in the normal human intestinal flora. You can grow with citrate as the only source of energy, which is also referred to by the generic name.

features

The cells of Citrobacter - types are characterized by flagella active movement ( motile ). They use various organic compounds as sources of energy and building materials in oxidative or fermentative energy metabolism . They are thus facultatively anaerobic . For example, they can utilize glucose and lactose with the formation of gas and acid, so they belong to the coliform bacteria . As for the products that are formed during fermentation , they belong to the type of bacteria that undergo mixed acid fermentation . A special feature is that they can grow with citrate, the anion of citric acid , as the only source of energy, as the generic name refers to. As is typical for Enterobacteriaceae, the catalase test is positive and the oxidase test is negative.

Biochemical features such as the enzymes present and the resulting metabolic properties can be used in a colorful series to identify Citrobacter species or to differentiate them from other representatives of the Enterobacteriaceae. The enzyme urease to break down urea is present in some species. The formation of hydrogen sulfide (H 2 S) also only occurs in some species. Nitrate is reduced to nitrite . The Voges-Proskauer reaction is negative, no acetoin is formed. The indole test is also negative. With the help of the IMViC tests, Citrobacter can be distinguished from Enterobacter and Escherichia .

The GC content , ie the proportion of the nucleobases guanine and cytosine in the bacterial DNA , is 50–52  mol percent .

Due to the phosphatase activity in their cell wall, Citrobacter species can precipitate plutonium [Pu (IV)] from aqueous solution and bind it as a lanthanum-phosphate complex.

Citrobacter species, like some other prokaryotes , are able to fix nitrogen . They are diazotrophic . C. freundii has been found in the intestines of Mediterranean fruit flies and it is believed that the nitrogen fixed by the bacteria is a relevant source of organic nitrogen for the insects. Thus, similar to the termites, the flies live in a symbiosis with their intestinal bacteria .

Occurrence

Citrobacter species are widespread in almost all habitats, such as the ground , in bodies of water and in sewage . They also occur as part of the intestinal flora in the human gastrointestinal tract .

Systematics

The genus Citrobacter belongs to the Enterobacteriaceae family ( Enterobacteria ) in the order of Enterobacteriales . This order belongs to the class of Gammaproteobacteria . The Enterobacteriaceae form a large group of gram-negative bacteria to which u. a. the genera Enterobacter , Escherichia , Klebsiella , Proteus , Raoultella , Salmonella , Serratia , Shigella and Yersinia belong, of which some representatives are important as pathogens.

Citrobacter was first described by Werkmann and Gillen in 1932 . The genus includes the following species (as of 2014):

Medical importance

As pathogens play Citrobacter TYPES rarely a role and may occur in patients with weakened immune systems as opportunistic pathogen infections cause (usually intra-abdominal infections). Mostly these are hospital infections ( nosocomial infections ). In individual cases, they have been described as causing infections outside the intestine (“extraintestinal”). Urinary tract infections and infections of the respiratory tract are mentioned as examples . In rare cases, Citrobacter species have also been detected in infant meningitis and sepsis .

For antimicrobial therapy (as of 2009), cefotaxime , ceftriaxone and, alternatively, ciprofloxacin and levofloxacin are available for infections with Citrobacter koseri . Citrobacter freundii is treated with imipenem , meropenem , ertapenem , quinolones or aminoglycosides .

Web links

Commons : Citrobacter  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e f Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel, 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 3-8274-0566-1 , pp. 531-536.
  2. ^ A b c Hans G. Schlegel, Christiane Zaborosch: General microbiology . 7th edition. Thieme Verlag, Stuttgart / New York 1992, ISBN 3-13-444607-3 , p. 307-313 .
  3. ^ A b c Herbert Hof, Rüdiger Dörries: Dual series: Medical microbiology . 3. Edition. Thieme Verlag, Stuttgart 2005, ISBN 978-3-13-125313-2 , p. 395 .
  4. ^ A b c Jean Euzéby, Aidan C. Parte: Genus Citrobacter. In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Retrieved August 9, 2014 .
  5. ↑ P. Yong, LE Macaskie: Bioaccumulation of Lanthanum, Uranium and Thorium, and Use of a Model System to develop a Method for the Biologically-mediated Removal of Plutonium from Solution. In: J. Chem. Technol. Biotechnol. , Vol. 71, 1998, pp. 15-26; Abstract .
  6. ↑ A. Behar, B. Yuval, E. Jurkevitch: Enterobacteria-mediated nitrogen fixation in natural populations of the fruit fly Ceratitis capitata. In: Molecular Ecology. Volume 14, 2005, pp. 2637-2643.
  7. ^ A b Dictionary editing of the publisher (ed.): Pschyrembel Clinical Dictionary (keyword “Citrobacter”) . 259th edition. Walter de Gruyter, Berlin 2002, ISBN 3-11-016522-8 , p. 299 .
  8. ↑ a b S. Suerbaum, J. Bockemühl, H. Karch: Enterobacteria . In: Helmut Hahn, Stefan HE Kaufmann, Thomas F. Schulz, Sebastian Suerbaum (eds.): Medical microbiology and infectious diseases . 6th edition. Springer Verlag, Heidelberg 2009, ISBN 978-3-540-46359-7 , p. 237-268 (here 250) .
  9. ^ Marianne Abele-Horn: Antimicrobial Therapy. Decision support for the treatment and prophylaxis of infectious diseases. With the collaboration of Werner Heinz, Hartwig Klinker, Johann Schurz and August Stich, 2nd, revised and expanded edition. Peter Wiehl, Marburg 2009, ISBN 978-3-927219-14-4 , p. 261.