Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 4 de 4
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Cell Microbiol ; 8(11): 1791-802, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16803581

RESUMO

Physiological adaptation of intracellular bacteria is critical for timely interaction with eukaryotic host cells. One mechanism of adaptation, the stringent response, is induced by nutrient stress via its effector molecule (p)ppGpp, synthesized by the action of RelA/SpoT homologues. The intracellular pathogen Brucella spp., causative agent of brucellosis, possesses a gene homologous to relA/spoT, named rsh, encoding a (p)ppGpp synthetase as confirmed by heterologous complementation of a relA mutant of Sinorhizobium meliloti. The Rsh deletion mutants in Brucella suis and Brucella melitensis were characterized by altered morphology, and by reduced survival under starvation conditions and in cellular and murine models of infection. Most interestingly, we evidenced that expression of virB, encoding the type IV secretion system, a major virulence factor of Brucella, was Rsh-dependent. All mutant phenotypes, including lack of VirB proteins, were complemented with the rsh gene of Brucella. In addition, RelA of S. meliloti functionally replaced Brucella Rsh, describing the capacity of a gene from a plant symbiont to restore virulence in a mammalian pathogen. We therefore concluded that in the intramacrophagic environment encountered by Brucella, Rsh might participate in the adaptation of the pathogen to low-nutrient environments, and indirectly in the VirB-mediated formation of the final replicative niche.


Assuntos
Proteínas de Bactérias/genética , Brucella melitensis/genética , Brucella suis/genética , Expressão Gênica/genética , Fatores de Virulência/genética , Animais , Proteínas de Bactérias/metabolismo , Brucella melitensis/patogenicidade , Brucella suis/patogenicidade , Brucelose/microbiologia , Células Cultivadas , Deleção de Genes , Regulação Bacteriana da Expressão Gênica/genética , Teste de Complementação Genética/métodos , Guanosina Tetrafosfato/genética , Guanosina Tetrafosfato/metabolismo , Células HeLa , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Mutação/genética , Ovinos , Fatores de Tempo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Virulência/genética , Fatores de Virulência/metabolismo
2.
Cell Microbiol ; 7(8): 1151-61, 2005 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16008582

RESUMO

Both a type IV secretion system and a flagellum have been described in Brucella melitensis. These two multimolecular surface appendages share several features. Their expression in bacteriological medium is growth curve dependent, both are induced intracellularly and are required for full virulence in a mouse model of infection. Here we report the identification of VjbR, a quorum sensing-related transcriptional regulator. A vjbR mutant has a downregulated expression of both virB operon and flagellar genes either during vegetative growth or during intracellular infection. In a cellular model, the vacuoles containing the vjbR mutant or a virB mutant are decorated with the same markers at similar times post infection. The vjbR mutant is also strongly attenuated in a mouse model of infection. As C(12)-homoserine lactone pheromone is known to be involved in virB repression, we postulated that VjbR is mediating this effect. In agreement with this hypothesis, we observed that, as virB operon, flagellar genes are controlled by the pheromone. All together these data support a model in which VjbR acts as a major regulator of virulence factors in Brucella.


Assuntos
Proteínas de Bactérias/biossíntese , Brucella melitensis/metabolismo , Flagelos/metabolismo , Fatores de Transcrição/biossíntese , Vacúolos/metabolismo , Fatores de Virulência/metabolismo , 4-Butirolactona/análogos & derivados , 4-Butirolactona/metabolismo , 4-Butirolactona/farmacologia , Animais , Proteínas de Bactérias/genética , Brucella melitensis/genética , Brucelose/metabolismo , Brucelose/microbiologia , Bovinos , Regulação para Baixo , Flagelos/genética , Células HeLa , Humanos , Técnicas In Vitro , Macrófagos/microbiologia , Camundongos , Mutação , Feromônios/metabolismo , Feromônios/farmacologia , Regiões Promotoras Genéticas , Fatores de Transcrição/genética , Fatores de Virulência/genética
3.
Infect Immun ; 72(10): 5783-90, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15385478

RESUMO

Brucella spp. are gram-negative intracellular facultative pathogens that are known to produce 2,3-dihydroxybenzoic acid (DHBA), a catechol siderophore that is essential for full virulence in the natural host. The mechanism of DHBA entry into Brucella and other gram-negative bacteria is poorly understood. Using mini-Tn5Kmcat mutagenesis, we created a transposon library of Brucella melitensis 16M and isolated 32 mutants with a defect in iron acquisition or assimilation. Three of these transposon mutants are deficient in utilization of DHBA. Analysis of these three mutants indicated that the ExbB, DstC, and DugA proteins are required for optimal assimilation of DHBA and/or citrate. ExbB is part of the Ton complex, and DstC is a permease homologue of an iron(III) ABC transporter; in gram-negative bacteria these two complexes are involved in the uptake of iron through the outer and inner membranes, respectively. DugA is a new partner in iron utilization that exhibits homology with the bacterial conserved GTPase YchF. Based on this homology, DugA could have a putative regulatory function in iron assimilation in Brucella. None of the three mutants was attenuated in cellular models or in the mouse model of infection, which is consistent with the previous suggestion that DHBA utilization is not required in these models.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Proteínas de Bactérias/metabolismo , Brucella melitensis/classificação , Brucella melitensis/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Ferro/metabolismo , Transportadores de Cassetes de Ligação de ATP/genética , Sequência de Aminoácidos , Animais , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Brucella melitensis/efeitos dos fármacos , Brucella melitensis/genética , Brucelose/microbiologia , Catecóis/metabolismo , Catecóis/farmacologia , Bovinos , Contagem de Colônia Microbiana , GTP Fosfo-Hidrolases/química , GTP Fosfo-Hidrolases/genética , Genes Bacterianos/genética , Células HeLa , Humanos , Hidroxibenzoatos , Ferro/antagonistas & inibidores , Quelantes de Ferro/farmacologia , Macrófagos/microbiologia , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Mutação/genética , Sideróforos/metabolismo , Sideróforos/farmacologia
4.
Infect Immun ; 70(10): 5540-6, 2002 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-12228280

RESUMO

The distinctive properties of Brucella outer membrane have been considered to be critical for Brucella sp. virulence. Among the outer membrane molecules possibly related to these properties, Omp10 and Omp19 are immunoreactive outer membrane lipoproteins. Moreover, these proteins of Brucella could constitute a new family of outer membrane proteins specifically encountered in the family RHIZOBIACEAE: We evaluated the impact of omp10 or omp19 deletion on Brucella abortus outer membrane properties and virulence in mice. The omp10 mutant was dramatically attenuated for survival in mice and was defective for growth in minimal medium but was not impaired in intracellular growth in vitro, nor does it display clear modification of the outer membrane properties. Significantly fewer brucellae were recovered from the spleens of mice infected with the omp19 mutant than from those of mice infected with the parent strain at 4 and 8 weeks postinfection. The omp19 mutant exhibited an increase in sensitivity to the polycation polymyxin B and to sodium deoxycholate. These results indicate that inactivation of the omp19 gene alters the outer membrane properties of B. abortus.


Assuntos
Antígenos de Bactérias , Proteínas da Membrana Bacteriana Externa/genética , Brucella abortus/genética , Brucella abortus/patogenicidade , Genes Bacterianos , Lipoproteínas , Animais , Proteínas da Membrana Bacteriana Externa/fisiologia , Brucella abortus/crescimento & desenvolvimento , Brucella abortus/fisiologia , Brucelose/etiologia , Brucelose/microbiologia , Bovinos , Linhagem Celular , Feminino , Deleção de Genes , Células HeLa , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Mutação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...