Lawsonia (genus of bacteria)

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Lawsonia
Systematics
Domain : Bacteria (bacteria)
Department : Proteobacteria
Class : Deltaproteobacteria
Order : Desulfovibrionales
Family : Desulfovibrionaceae
Genre : Lawsonia
Scientific name
Lawsonia
McOrist et al. (1995)

Lawsonia is a genus of Gram-negative bacteria with only one species, Lawsonia intracellularis . The dimensions of the curved, sometimes straight, rod-shaped cells are approximately 0.25 - 0.5 × 1.25 - 1.75 μm. The cells are immobile and growstrictly intracellularly in a microaerophilic atmosphere. Only cell media are therefore suitable for cultivation. Enrichment takes place in the rat enterocyte cell line IEC-18 and in the intestinal epithelial cell line Henle 407.

Pathogenicity and life cycle

Lawsonia intracellularis is pathogenic to pigs and causes the diarrheal disease porcine proliferative enteritis . Thespecies has also been detectedin horses , sheep , rabbits , rats , foxes , white-tailed deer and ostriches .

After the bacterium has attached to the outer cell membranes of the host's enterocytes, it is phagocytosed a short time later . After up to approx. 3 hours the vacuole formed by phagocytosis dissolves, the bacterium is now free in the cytoplasm of the host cell and begins to multiply. The bacterium then appears mainly apically in the infected epithelial cells of the intestine ( enterocytes ). But it is also found sporadically in deeper layers such as the muscularis. Granulomas were also described in monkeys as part of the infection. The life cycle is similar to that of Orientia tsutsugamushi , the Rickettsiaceae causative agent of Tsutsugamushi fever .

Systematics

So far Lawsonia intracellularis is the only species in the genus. Surprisingly, DNA tests revealed Helicobacter to be the closest relative. Although Lawsonia is part of the Desulfovibrionaceae family , the bacterium is not a desulfurizer . These free-living bacteria, also known as sulphate bacteria, gain energy from the reduction of the sulphate (SO 4 2− ) they have absorbed themselves to sulphide (sulphide ion S 2− ). Lawsonia, on the other hand, is completely dependent on the host. The genus Bilophila, which belongs to the same family, is also not one of the sulfate-reducing bacteria; it was found in patients with appendicitis, among other things. The three genera were placed in the same family on the basis of the results of DNA studies, despite the differences in metabolism and lifestyle.

In older literature the bacterium can also be found under the name “Campylobacter-like bacterium”. Furthermore, Lawsonia is also the scientific genus name of the plant genus henna . For the species Lawsonia intracellularis McOrist et al. 1995 are (or were) also the designations " Candidatus intracellularis" Murray and Stackebrandt 1995 and "Ileal symbiont intracellularis" Gebhart et al. 1993 common.

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  • Medical microbiology, infection and epidemic theory von Rolle / Mayr, Enke Verlag Stuttgart (2007)
  • Michael T. Madigan, John M. Martinko, Jack Parker: Brock - Microbiology . 11th edition. Pearson Studium, Munich 2006, ISBN 3-8274-0566-1 .
  • George M. Garrity: Bergey's manual of systematic bacteriology . 2nd Edition. Springer, New York 2005, Vol. 2: The Proteobacteria Part C: The Alpha-, Beta-, Delta-, and Epsilonproteabacteria. ISBN 0-387-24145-0 .
  • Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer, Erko Stackebrandt (Eds.): The Prokaryotes, A Handbook of the Biology of Bacteria . 7 volumes, 3rd edition, Springer-Verlag, New York et al. O. 2006, ISBN 0-387-30740-0 . Vol. 2: Ecophysiology and Biochemistry. ISBN 0-387-2549-27 .
  • JP Euzéby: List of Prokaryotic Names with Standing in Nomenclature - Genus Lawsonia

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