RESUMO
The genome of Brucella melitensis contains genes coding for the sigma factors RpoD, RpoN, RpoH1, RpoH2, RpoE1 and RpoE2. Previously published data show that B. melitensis is flagellated and that an rpoE1 mutant overexpresses the flagellar protein FlgE. In this study, we demonstrate that mutation of rpoE1 causes an overexpression of the flagellar genes fliF, flgE, fliC, flaF and flbT, correlating with the production of a longer filament and thereby demonstrating that RpoE1 acts as a flagellar repressor. Moreover, mutation of rpoE1 increases the promoter activity of the flagellar master regulator ftcR, suggesting that RpoE1 acts upstream of ftcR. Together, these data show that RpoE1 represses the flagellar synthesis and filament length in B. melitensis.
Assuntos
Proteínas de Bactérias/metabolismo , Brucella melitensis/metabolismo , Flagelos/metabolismo , Regulação Bacteriana da Expressão Gênica , Proteínas Repressoras/metabolismo , Fator sigma/metabolismo , Proteínas de Bactérias/genética , Brucella melitensis/genética , Flagelos/genética , Mutação , Transporte Proteico , Proteínas Repressoras/genética , Fator sigma/genéticaRESUMO
B. melitensis 16M genome analysis revealed the presence of six putative sigma factor-encoding genes: rpoD, rpoH1, rpoH2, rpoE1, rpoE2, and rpoN. We mutated all these genes except rpoD. Phenotypic analysis of the mutants reveals that a strain carrying an rpoH2 null mutation (DeltarpoH2) is impaired for growth at 21 and 42 degrees C and shows increased sensitivity to hydrogen peroxide. Compared to the wild-type strain, the DeltarpoH2 mutant is attenuated in all virulence models tested. Three other null mutants (DeltarpoH1, DeltarpoE1, and DeltarpoE2 mutants) are also defective for survival in mice at 4 weeks postinfection. We also demonstrated that rpoH2 deletion strongly reduces the expression of two major virulence factors in B. melitensis, the type IV secretion system and the flagellum.
Assuntos
Adaptação Fisiológica/genética , Brucella melitensis/patogenicidade , Regulação Bacteriana da Expressão Gênica , Proteínas de Choque Térmico/fisiologia , Fator sigma/fisiologia , Virulência/genética , Animais , Antibacterianos/farmacologia , Western Blotting , Brucella melitensis/genética , Brucella melitensis/crescimento & desenvolvimento , Brucelose , Linhagem Celular , Modelos Animais de Doenças , Células Epiteliais/microbiologia , Deleção de Genes , Proteínas de Choque Térmico/genética , Humanos , Peróxido de Hidrogênio/farmacologia , Macrófagos/microbiologia , Camundongos , Camundongos Endogâmicos BALB C , Mutagênese Insercional , Fator sigma/genética , Temperatura , Fatores de Virulência/biossínteseRESUMO
Numerous pathogenic bacteria contain luxS, which is required for autoinducer-2 production. Here, we demonstrate that Neisseria meningitidis contains a functional copy of luxS that is necessary for full meningococcal virulence; strains with a luxS deletion are defective for bacteremia, a prerequisite of meningococcal pathogenesis.