title: A low G+C content genetic island in Mycobacterium avium subsp. paratuberculosis and M. avium subsp. silvaticum with homologous genes in Mycobacterium tuberculosis.
abstract: The technique of representation difference analysis PCR has been applied to find genes specific to Mycobacterium avium subsp. paratuberculosis. This generated a 671 bp fragment which was used to isolate a larger genetic element found in the enteric pathogens M. avium subsp. paratuberculosis and M. avium subsp. silvaticum but which was absent from the very closely related and relatively benign M. avium subsp. avium. This element, designated GS, is greater than 6.5 kbp in length and has a G+C content 9 mol% lower than other genes from this species. There is a previously uncharacterized insertion sequence associated with one end. The GS element encodes five ORFs in M. avium subsp. paratuberculosis and M. avium subsp. silvaticum, all of which have counterparts encoded in Mycobacterium tuberculosis. Database searches revealed homologues for these ORFs in a number of bacterial species, predominantly Gram-negative organisms, including a number of enteric pathogens. These homologous genes encode functions related to LPS or extracellular polysaccharide biosynthesis. This element has a number of features in common with pathogenicity islands such as its low G+C content, an association with a putative insertion sequence and a grouping of genes of related function with a possible link to virulence. No direct link to pathogenicity has been shown but GS may belong to a group of related 'genetic islands' and represents the first such element to be identified in mycobacteria.
authors.forename: Mark
authors.initials: M
authors.lastname: Tizard
authors.forename: Tim
authors.initials: T
authors.lastname: Bull
authors.forename: Douglas
authors.initials: D
authors.lastname: Millar
authors.forename: Tim
authors.initials: T
authors.lastname: Doran
authors.forename: Helene
authors.initials: H
authors.lastname: Martin
authors.forename: Nazira
authors.initials: N
authors.lastname: Sumar
authors.forename: Jon
authors.initials: J
authors.lastname: Ford
authors.forename: John
authors.initials: J
authors.lastname: Hermon-Taylor
mesh_terms: D002473:Cell Wall / Q000737:chemistry; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018899:CpG Islands; D004269:DNA, Bacterial / Q000032:analysis; D015226:Dinucleoside Phosphates / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009162:Mycobacterium avium / Q000145:classification / Q000235:genetics*; D016927:Mycobacterium avium subsp. paratuberculosis / Q000235:genetics*; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D004269:DNA, Bacterial; D015226:Dinucleoside Phosphates; C015772:CpG dinucleotide