RESUMO
We report the complete and annotated genome sequence of the nonpathogenic Listeria seeligeri SLCC3954 serovar 1/2b type strain harboring the smallest completely sequenced genome of the genus Listeria.
Assuntos
DNA Bacteriano/química , DNA Bacteriano/genética , Genoma Bacteriano , Listeria/genética , Dados de Sequência Molecular , Análise de Sequência de DNARESUMO
We present the complete genome sequence of Listeria welshimeri, a nonpathogenic member of the genus Listeria. Listeria welshimeri harbors a circular chromosome of 2,814,130 bp with 2,780 open reading frames. Comparative genomic analysis of chromosomal regions between L. welshimeri, Listeria innocua, and Listeria monocytogenes shows strong overall conservation of synteny, with the exception of the translocation of an F(o)F(1) ATP synthase. The smaller size of the L. welshimeri genome is the result of deletions in all of the genes involved in virulence and of "fitness" genes required for intracellular survival, transcription factors, and LPXTG- and LRR-containing proteins as well as 55 genes involved in carbohydrate transport and metabolism. In total, 482 genes are absent from L. welshimeri relative to L. monocytogenes. Of these, 249 deletions are commonly absent in both L. welshimeri and L. innocua, suggesting similar genome evolutionary paths from an ancestor. We also identified 311 genes specific to L. welshimeri that are absent in the other two species, indicating gene expansion in L. welshimeri, including horizontal gene transfer. The species L. welshimeri appears to have been derived from early evolutionary events and an ancestor more compact than L. monocytogenes that led to the emergence of nonpathogenic Listeria spp.
Assuntos
DNA Bacteriano/genética , Evolução Molecular , Genoma Bacteriano , Listeria/genética , Análise de Sequência de DNA , Cromossomos Bacterianos/genética , DNA Bacteriano/química , Deleção de Genes , Ordem dos Genes , Transferência Genética Horizontal , Listeria monocytogenes/genética , ATPases Mitocondriais Próton-Translocadoras/genética , Dados de Sequência Molecular , Fases de Leitura Aberta , Filogenia , Sintenia , Translocação GenéticaRESUMO
The genus Listeria contains the two pathogenic species Listeria monocytogenes and Listeria ivanovii and the four apparently apathogenic species Listeria innocua, Listeria seeligeri, Listeria welshimeri, and Listeria grayi. Pathogenicity of the former two species is enabled by an approximately 9 kb virulence gene cluster which is also present in a modified form in L. seeligeri. For all Listeria species, the sequence of the virulence gene cluster locus and its flanking regions was either determined in this study or assembled from public databases. Furthermore, some virulence-associated internalin loci were compared among the six species. Phylogenetic analyses were performed on a data set containing the sequences of prs, ldh, vclA, and vclB (all directly flanking the virulence gene cluster), as well as the iap gene and the 16S and 23S-rRNA coding genes which are located at different sites in the listerial chromosomes. L. grayi represents the deepest branch within the genus. The remaining five species form two groupings which have a high bootstrap support and which are consistently found by using different treeing methods. One lineage represents L. monocytogenes and L. innocua, while the other contains L. welshimeri, L. ivanovii and L. seeligeri, with L. welshimeri forming the deepest branch. Based on this perception, we tried to reconstruct the evolution of the virulence gene cluster. Since no traces of lateral gene transfer events could be detected the most parsimonious scenario is that the virulence gene cluster was present in the common ancestor of L. monocytogenes, L. innocua, L. ivanovii, L. seeligeri and L. welshimeri and that the pathogenic capability has been lost in two separate events represented by L. innocua and L. welshimeri. This hypothesis is also supported by the location of the putative deletion breakpoints of the virulence gene cluster within L. innocua and L. welshimeri.
Assuntos
Evolução Molecular , Listeria/genética , Listeria/patogenicidade , Filogenia , Fatores de Virulência/genética , Proteínas de Bactérias/genética , DNA Bacteriano/química , DNA Ribossômico/química , DNA Ribossômico/genética , Deleção de Genes , Genes Bacterianos/genética , Genes de RNAr , Lipoproteínas/genética , Dados de Sequência Molecular , Família Multigênica , RNA Ribossômico 16S/genética , RNA Ribossômico 23S/genética , Análise de Sequência de DNA , Virulência/genéticaRESUMO
Based on molecular typing methods, we identified a rare case of a recurrent L. monocytogenes infection resulting from an infected aortic prosthesis as detected by 18-F-Fluoro-d-deoxyglucose positron emission tomography (FDG PET). Our case highlights the usefulness of molecular typing and nuclear imaging methods for understanding L. monocytogenes pathogenesis and epidemiology.
Assuntos
Prótese Vascular/efeitos adversos , Listeria monocytogenes/isolamento & purificação , Listeriose/diagnóstico , Dissecção Aórtica/diagnóstico , Dissecção Aórtica/cirurgia , Aneurisma da Aorta Torácica/diagnóstico , Aneurisma da Aorta Torácica/cirurgia , Sequência de Bases , DNA Bacteriano/análise , Humanos , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Reação em Cadeia da Polimerase/métodos , Prognóstico , Recidiva , Sensibilidade e Especificidade , Procedimentos Cirúrgicos Vasculares/efeitos adversos , Procedimentos Cirúrgicos Vasculares/métodosRESUMO
The genes encoding subunits A and B of DNA gyrase and subunits C and E of topoisomerase IV of Listeria monocytogenes, gyrA, gyrB, parC and parE, respectively, were cloned and sequenced. Compared with the sequences of quinolone-susceptible bacteria, such as Escherichia coli and Bacillus subtilis, the quinolone resistance-determining region (QRDR) of DNA gyrase subunit A was altered; the deduced amino acid sequences revealed the substitutions Ser-84-->Thr and Asp/Glu-88-->Phe, two amino acid variations at hot spots, commonly associated with resistance to quinolones. No relevant divergences from QRDR consensus sequences were observed in GyrB or both topoisomerase IV subunits. Thus, it could be argued that the amino acid substitutions in GyrA would explain the intrinsic resistance of L. monocytogenes to nalidixic acid. In order to analyse the actual role of the GyrA alterations, a plasmid-encoded gyrA allele was mutated and transformed into L. monocytogenes. However, these heterodiploid strains were not affected in their resistance to nalidixic acid. The effects of the mutant plasmids on ciprofloxacin and sparfloxacin susceptibility were only modest.
