A spontaneous genomic deletion in Listeria ivanovii identifies LIPI-2, a species-specific pathogenicity island encoding sphingomyelinase and numerous internalins

Gustavo Domínguez-Bernal, Stefanie Müller-Altrock, Bruno González-Zorn, Mariela Scortti, Petra Herrmann, Hector J Monzó, Lizeth Lacharme, Jürgen Kreft, Jose A Vazquez-Boland

Research output: Contribution to journalArticlepeer-review

Abstract

Listeria ivanovii differs from the human pathogen Listeria monocytogenes in that it specifically affects ruminants, causing septicaemia and abortion but not meningo-encephalitis. The genetic characterization of spontaneous L. ivanovii mutants lacking the virulence factor SmcL (sphingomyelinase) led us to identify LIPI-2, the first species-specific pathogenicity island from Listeria. Besides SmcL, this 22 kb chromosomal locus encodes 10 internalin (Inl) proteins: i-InlB1 and -B2 are large/surface-associated Inls similar to L. monocytogenes InlB; i-InlE to -L are small/excreted (SE)-Inls, i-InlG being a tandem fusion of two SE-Inls. Except i-inlB1, all LIPI-2 inl genes are controlled by the virulence regulator, PrfA. LIPI-2 is inserted into a tRNA locus and is unstable - half of it deleting at approximately 10(-4) frequency with a portion of contiguous DNA. The spontaneous mutants were attenuated in vivo in mice and lambs and showed impaired intracellular growth and apoptosis induction in bovine MDBK cells. Targeted knock-out mutations associated the virulence defect with LIPI-2 genes. The region between the core genome loci ysnB-tRNA(arg) and ydeI flanking LIPI-2 contained different gene complements in the different Listeria spp. and even serovars of L. monocytogenes, including remnants of the PSA bacteriophage int gene in serovar 4b, indicating it is a hot spot for horizontal genome diversification. LIPI-2 is conserved in L. ivanovii ssp. ivanovii and londoniensis, suggesting an early acquisition during the species' evolution. LIPI-2 is likely to play an important role in the pathogenic and host tropism of L. ivanovii.
Original languageEnglish
Pages (from-to)415-32
JournalMolecular Microbiology
Volume59
Issue number2
DOIs
Publication statusPublished - Jan 2006

Keywords

  • Bacterial Proteins/genetics
  • Base Sequence
  • Chromosome Mapping
  • Gene Deletion
  • Genes, Bacterial
  • Genome, Bacterial
  • Listeria/genetics
  • Listeria/pathogenicity
  • Sphingomyelin Phosphodiesterase/genetics
  • Virulence/genetics

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