A Microbial Biorealm page on the genus Lawsonia intracellularis
Higher order taxa
Bacteria; Proteobacteria; Deltaproteobacteria; Desulfovibrionales; Desulfovibrionaceae; Lawsonia.
Genus species: Lawsonia intracellularis
Description and significance
Lawsonia intracellularis is a bacterial pathogen which causes disease in a wide range of animals, mainly pigs. The bacterial pathogen invades the intestinal epithelial cells which causes hyperplasia of the infected cells which leads to the process of disease pathogenesis. Lawsonia intracelluaris is an intracellular enterophathogen that is the cause of intestinal hyperplasia which is an abnormal increase in the number of cells in an organ or a tissue with consequent enlargement.
The disease has two clinical manifestations in pigs: an acute hemorrhagic form often called porcine hemorrhagic enteropathy, and a more chronic proliferative form often referred as porcine intestinal adenomatosis.
This includes proliferative enteropathy, intestinal adenomatosis, and ileitis. Lawsonia intracellularis though primarily recognized in pigs, is spreading to a wide range of mammals. With a 16SrRNA gene sequence, Lawsonia intracellularis is related to Desulfovibio, a sulfate-reducing bacteria and Bilophila wadsworthia.
Lawsonia intracellularis is made up of a circular chromosome and the length is 1,457,619 nucleotides. The genomic content includes 1,719,014 nucleotides. It had 1, 337 protein genes and 49 RNA genes.
Cell structure and metabolism
The structure of Lawsonia intracellularis reveals non-spore-forming curved rods. It contains gram-negative cells that are able to retain carbol-fushsin when stained using the Ziehl-Neelsen method. It is nonpigmented and nonflagellated. Through the Ziehl-Neelsen method the cell wall of a gram-negative is shown as well as the protoplasmic structure of a prokaryote. The cells replicate within the cytoplasm and are not enclosed by membrane-bound vacuoles. This occurs in epithilial cells of pigs.
Natural infection has not been detected in either wild or laboratory mice however, the former represent a potential reservoir, therefore studies have further implications for the ecology and epidemiology of PE, particularly in pigs. The environment is more likely to be cohabited by rodents. Though the major animal that is most susceptible are pigs, it is becoming more apparent that Lawsonia intracellularis has a broad host range which is wider than currently known. Though there is evidence of infection in primates, there is currently no direct evidence that Lawsonia intracellularis can infect humans, although one report has suggested a link with human disease.
Lawsonia intracellularis is an intracellular bacterial pathogen which cause intestinal hyperplasia in a wide range of mammalian and avian species.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
"Single-chain antibodies (scFv) exhibiting specific binding to Lawsonia intracellularis were isolated from a phagemid library expressing scFvs molecules on the surface of filamentous bacteriophages. For scFv selection whole bacterial cells were used and individual clones were tested in ELISA test. The total of seven unique clones with different fingerprint profiles was isolated. All clones were able to bind specifically in immunofluorescence assay. This is the first report of species specific recombinant antibodies against L. intracellularis".
"An in situ hybridization (ISH) procedure with a digoxigenin-labeled oligonucleotide probe for detection of Lawsonia intracellularis in paraffin-embedded tissue is described. This technique recognized 71% of PCR-positive cases and was thus superior to Warthin-Starry silver stain, which only detected 41%. The presented ISH is of comparable sensitivity to previously published immunohistochemical assays and is recommended for laboratories wishing to diagnose L. intracellularis infections in tissue sections but without access to antibodies".
1) Mcorist, S., Gebhart, C.J., Boid, R., Barns, S.M. “Characterization of Lawsonia intracellularis gen. nov., sp. nov., the Obligately Intracellular Bacterium of Porcine Proliferative Enteropathy.” 1995. Volume 45. p. 820-825.
2) Smith, DG.E., Mitchell, S.C., Nash, T., Rhind, S. “Gamma Interferon Influences Intestinal Epithelial Hyperplasia Caused by Lawsonia intracellularis Infection in Mice.” 2000. Volume 68. p. 6737–6743.
3) Jones, G. F., Ward, G.E., Murtaugh, M.P., Lin, G. and Gebhart, C.J. “Qualitative detection of Lawsonia intracellularis bacteria by PCR.” 2007.
4) NCBI Taxonomy Genome Project, http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=363253&lvl=3&lin=f&keep=1&srchmode=1&unlock.