A spontaneous genomic deletion in Listeria ivanovii identifies LIPI-2, a species-specific pathogenicity island encoding sphingomyelinase and numerous internalins.
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.
Domínguez-Bernal
Gustavo
G
Grupo de Patogénesis Molecular Bacteriana, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.
Müller-Altrock
Stefanie
S
González-Zorn
Bruno
B
Scortti
Mariela
M
Herrmann
Petra
P
Monzó
Héctor J
HJ
Lacharme
Lizeth
L
Kreft
Jürgen
J
Vázquez-Boland
José A
JA
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D017353:Gene Deletion; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D008087:Listeria / Q000235:genetics* / Q000472:pathogenicity; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics*; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D013108:Sphingomyelin Phosphodiesterase