RESUMEN
Staphylococcus argenteus (S. argenteus) is a newly identified Staphylococcus species that has been misidentified as Staphylococcus aureus (S. aureus) and is clinically relevant. We identified 25 S. argenteus genomes in our collection of whole genome sequenced S. aureus. These genomes were compared to publicly available genomes and a phylogeny revealed seven clusters corresponding to seven clonal complexes. The genome of S. argenteus was found to be different from the genome of S. aureus and a core genome analysis showed that ~33% of the total gene pool was shared between the two species, at 90% homology level. An assessment of mobile elements shows flow of SCCmec cassettes, plasmids, phages, and pathogenicity islands, between S. argenteus and S. aureus. This dataset emphasizes that S. argenteus and S. aureus are two separate species that share genetic material.
RESUMEN
Peroxiredoxins contribute to protection of some bacteria against reactive oxygen intermediates (ROIs) and reactive nitrogen intermediates (RNIs). Listeria monocytogenes, a facultative intracellular bacterial pathogen, interacts with ROIs and RNIs during infection. In this study, we investigated the involvement of the 2-Cys peroxiredoxin (Prx) homologue in L. monocytogenes in the protection against ROIs and RNIs and in virulence through the construction of an in-frame prx deletion mutant. The Δprx mutant had increased sensitivity to hydrogen peroxide and cumene hydroperoxide compared to the wild-type strain. The mutant also exhibited an increased susceptibility to the nitric oxide-generating compound S-nitroso-N-acetylpenicillamine (SNAP) and 3-morpholinosydnonimine hydrochloride (SIN-1), a peroxynitrite donor. Furthermore, a diminished virulence of the Δprx mutant relative to the wild-type was observed in C57BL/6 mice, but not in inducible nitric oxide synthase-deficient mice. The results suggest that Prx protects L. monocytogenes against oxidative and nitrosative stress in vitro and in vivo and that the prx-encoded polypeptide thereby is involved in L. monocytogenes virulence.
Asunto(s)
Listeria monocytogenes/genética , Listeria monocytogenes/metabolismo , Estrés Oxidativo/genética , Peroxirredoxinas/genética , Peroxirredoxinas/metabolismo , Virulencia/genética , Animales , Peróxido de Hidrógeno/metabolismo , Ratones , Ratones Endogámicos C57BL , Óxido Nítrico/genética , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo II/genética , Óxido Nítrico Sintasa de Tipo II/metabolismo , Especies de Nitrógeno Reactivo/metabolismo , Especies Reactivas de Oxígeno/metabolismo , S-Nitroso-N-Acetilpenicilamina/metabolismoRESUMEN
Despite its prominent role as an intracellular human pathogen, Listeria monocytogenes normally features a saprophytic lifestyle, and shares many environmental habitats with predatory protozoa. Earlier studies claimed that Acanthamoeba may act as environmental reservoirs for L. monocytogenes, whereas others failed to confirm this hypothesis. Our findings support the latter and provide clear evidence that L. monocytogenes is unable to persist in Acanthamoeba castellanii and A. polyphaga. Instead, external Listeria cells are rapidly immobilized on the surface of Acanthamoeba trophozoites, forming large aggregates of densely packed bacteria that we termed backpacks. While the assembly of backpacks is dependent on bacterial motility, flagellation alone is not sufficient. Electron micrographs showed that the aggregates are held together by filaments of likely amoebal origin. Time-lapse microscopy revealed that shortly after the bacteria are collected, the amoeba can change direction of movement, phagocytose the backpack and continue to repeat the process. The phenomenon was also observed with avirulent L. monocytogenes mutants, non-pathogenic Listeria, and other motile bacteria, indicating that formation of backpacks is not specific for L. monocytogenes, and independent of bacterial pathogenicity or virulence. Hence, backpacking appears to represent a unique and highly effective strategy of Acanthamoeba to trap and feed on motile bacteria.
Asunto(s)
Acanthamoeba/microbiología , Listeria monocytogenes/fisiología , Fagocitosis , Bacterias/metabolismo , Listeria monocytogenes/crecimiento & desarrollo , Viabilidad MicrobianaRESUMEN
Listeria monocytogenes (L. monocytogenes) can cause fatal brainstem encephalitis in both sheep and humans. Here we review evidence that the bacteria can be incorporated into axons following a primary cycle of replication in macrophages/dendritic cells after subcutaneous injection in projection areas of peripheral neurons. The molecular mechanisms for the rocketing of L. monocytogenes in the cytosol by asymmetric cometic tails and the utility of this phenomenon for bacterial migration intraaxonally both in retro- and in anterograde directions to reach the central nervous system are described. The role of the immune response in the control of L. monocytogenes spread through peripheral neurons is highlighted, and a mechanism by which bacteria may be killed inside infected neurons through a nitric oxide-dependent pathway is pointed out.
Asunto(s)
Transporte Axonal/fisiología , Axones/microbiología , Listeria monocytogenes/patogenicidad , Neuronas/microbiología , Animales , Axones/metabolismo , Axones/patología , Células Dendríticas/citología , Humanos , Células Asesinas Naturales/fisiología , Listeria monocytogenes/fisiología , Macrófagos/citología , Óxido Nítrico/fisiologíaRESUMEN
The degU (lmo2515) gene encodes a putative response regulator in the food-borne pathogen Listeria monocytogenes. It has 63% amino acid identity to the DegU response regulator of Bacillus subtilis. We have characterized the degU gene product in L. monocytogenes EGD by generation of a deletion mutant. The DeltadegU mutant was found to be non-motile in motility plate assay and no flagellin was detected. The mutant was attenuated in challenge of mice. Northern blot analysis suggested that the degU gene product is a transcriptional activator of the flagellin gene, flaA, at 25 degrees C. However, the degU gene product had no influence on the transcription of prfA encoding the major virulence regulator, PrfA. The results indicate that the putative DegU response regulator is a pleiotropic regulator involved in expression of both motility at low temperature and in vivo virulence in mice.
Asunto(s)
Proteínas Bacterianas/fisiología , Listeria monocytogenes/fisiología , Listeria monocytogenes/patogenicidad , Adaptación Fisiológica , Animales , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Secuencia de Bases , Modelos Animales de Enfermedad , Femenino , Flagelina/análisis , Flagelina/genética , Flagelina/metabolismo , Eliminación de Gen , Regulación Bacteriana de la Expresión Génica , Genes Bacterianos , Genes Reguladores , Listeria monocytogenes/genética , Ratones , Ratones Endogámicos BALB C , Datos de Secuencia Molecular , Movimiento , Factores de Terminación de Péptidos , Transactivadores/genética , Transactivadores/metabolismo , Activación TranscripcionalRESUMEN
The flagellum protein flagellin of Listeria monocytogenes is encoded by the flaA gene. Immediately downstream of flaA, two genes, cheY and cheA, encoding products with homology to chemotaxis proteins of other bacteria, are located. In this study we constructed deletion mutants with mutations in flaA. cheY, and cheA to elucidate their role in the biology of infection with L. monocytogenes. The DeltacheY, DeltacheA, and double-mutant DeltacheYA mutants, but not DeltaflaA mutant, were motile in liquid media. However, the DeltacheA mutant had impaired swarming and the DeltacheY and DeltacheYA mutants were unable to swarm on soft agar plates, suggesting that cheY and cheA genes encode proteins involved in chemotaxis. The DeltaflaA, DeltacheY, DeltacheA, and DeltacheYA mutants (grown at 24 degrees C) showed reduced association with and invasion of Caco-2 cells compared to the wild-type strain. However, spleens from intragastrically infected BALB/c and C57BL/6 mice showed larger and similar numbers of the DeltaflaA and DeltacheYA mutants, respectively, compared to the wild-type controls. Such a discrepancy could be explained by the fact that tumor necrosis factor receptor p55 deficient mice showed dramatically exacerbated susceptibility to the wild-type but unchanged or only slightly increased levels of the DeltaflaA or DeltacheYA mutant. In summary, we show that listerial flaA. cheY, and cheA gene products facilitate the initial contact with epithelial cells and contribute to effective invasion but that flaA could also be involved in the triggering of immune responses.
Asunto(s)
Proteínas Bacterianas/metabolismo , Quimiotaxis , Flagelina/metabolismo , Regulación Bacteriana de la Expresión Génica , Listeria monocytogenes/patogenicidad , Proteínas de la Membrana/metabolismo , Transducción de Señal , Animales , Adhesión Bacteriana , Proteínas Bacterianas/genética , Células CACO-2 , Femenino , Flagelos/metabolismo , Flagelina/genética , Eliminación de Gen , Humanos , Listeria monocytogenes/fisiología , Listeriosis/microbiología , Proteínas de la Membrana/genética , Proteínas Quimiotácticas Aceptoras de Metilo , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , VirulenciaRESUMEN
CD44 has been implicated in immune and inflammatory processes. We have analyzed the role of CD44 in the outcome of Listeria monocytogenes infection in murine bone marrow-derived macrophages (BMM). Surprisingly, a dramatically decreased intracellular survival of L. monocytogenes was observed in CD44(-/-) BMM. CD44(-/-) heart or lung fibroblast cultures also showed reduced bacterial levels. Moreover, livers from CD44(-/-)-infected mice showed diminished levels of L. monocytogenes. In contrast, intracellular growth of Salmonella enterica serovar Typhimurium was the same in CD44(-/-) and control BMM. The CD44-mediated increased bacterial proliferation was not linked to altered BMM differentiation or to secretion of soluble factors. CD44 did not mediate listerial uptake, and it played no role in bacterial escape from the primary phagosome or formation of actin tails. Furthermore, CD44-enhanced listerial proliferation occurred in the absence of intracellular bacterial spreading. Interestingly, coincubation of BMM with hyaluronidase or anti-CD44 antibodies that selectively inhibit hyaluronan binding increased intracellular listerial proliferation. Treatment of cells with hyaluronan, in contrast, diminished listerial growth and induced proinflammatory transcript levels. We suggest that L. monocytogenes takes advantage of the CD44-mediated signaling to proliferate intracellularly, although binding of CD44 to certain ligands will inhibit such response.
Asunto(s)
Receptores de Hialuranos/fisiología , Listeria monocytogenes/crecimiento & desarrollo , Animales , Células de la Médula Ósea/microbiología , Macrófagos/microbiología , Ratones , Ratones Endogámicos C57BLRESUMEN
By using mice genomically lacking the mononuclear phagocytic growth factor colony-stimulating factor 1 and thereby deficient in macrophage and dendritic cell populations, we show that these cells play a dual role: they constitute a major defense against systemic infection but also facilitate cerebral bacterial invasion by Listeria monocytogenes.