RESUMO
The oligopeptide permease (Opp) cassette, an oligopeptide transport system belongs to the superfamily of ATP-binding cassette (ABC) transporter, is widely distributed in bacteria, including Streptococcus suis (S. suis). It is encoded by the opp operon containing oppA, oppB, oppC, oppD, and oppF. In addition to the uptake of peptide, the oppA gene also plays an important role in virulence of many pathogens. In this study, an oppA homologue from the highly virulent S. suis serotype 2 (S. suis 2) strain 05ZYH33 was identified. Flow cytometry and Western blot confirmed that OppA is a surface immunogenic protein and is expressed during S. suis 2 infection. To explore the role of oppA in S. suis 2 growth and pathogenicity, an isogenic 05ZYH33 mutant of oppA (â³oppA) was obtained by homologous recombination. Although the complementary strain was not obtained due to the â³oppA strain is not transformable, the current data revealed that deletion of the oppA gene in S. suis 2 has greatly affected its growth and virulence. Our data revealed that the growth rate is significantly slow for the â³oppA. Adherence of the â³oppA strain to human epithelial cells is greatly reduced comparing to the wild strain. Mouse infection experiment showed that inactivation of oppA greatly attenuated the high pathogenicity of S. suis 2. The observed results suggest that OppA is a surface-exposed protein and plays important roles in the growth and pathogenicity of S. suis 2.
Assuntos
Proteínas de Bactérias/genética , Proteínas de Bactérias/fisiologia , Proteínas de Transporte/genética , Proteínas de Transporte/fisiologia , Lipoproteínas/genética , Lipoproteínas/fisiologia , Streptococcus suis/genética , Streptococcus suis/metabolismo , Fatores de Virulência/genética , Fatores de Virulência/fisiologia , Sequência de Aminoácidos , Animais , Antígenos de Superfície/genética , Antígenos de Superfície/imunologia , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/metabolismo , Proteínas de Transporte/isolamento & purificação , Células Epiteliais/microbiologia , Feminino , Regulação Bacteriana da Expressão Gênica , Recombinação Homóloga , Humanos , Lipoproteínas/isolamento & purificação , Proteínas de Membrana/genética , Proteínas de Membrana/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Óperon , Alinhamento de Sequência , Infecções Estreptocócicas/genética , Streptococcus suis/crescimento & desenvolvimento , Streptococcus suis/patogenicidade , Fatores de Virulência/isolamento & purificaçãoRESUMO
Streptococcus suis serotype 2 is an emerging zoonotic pathogen responsible for a wide range of life-threatening diseases in pigs and humans. However, the pathogenesis of S. suis serotype 2 infection is not well understood. In this study, we report that an orphan response regulator, CovR, globally regulates gene expression and negatively controls the virulence of S. suis 05ZYH33, a streptococcal toxic shock syndrome (STSS)-causing strain. A covR-defective (DeltacovR) mutant of 05ZYH33 displayed dramatic phenotypic changes, such as formation of longer chains, production of thicker capsules, and increased hemolytic activity. Adherence of the DeltacovR mutant to epithelial cells was greatly increased, and its resistance to phagocytosis and killing by neutrophils and monocytes was also significantly enhanced. More importantly, inactivation of covR increased the lethality of S. suis serotype 2 in experimental infection of piglets, and this phenotype was restored by covR complementation. Colonization experiments also showed that the DeltacovR mutant exhibited an increased ability to colonize susceptible tissues of piglets. The pleiotropic phenotype of the DeltacovR mutant is in full agreement with the large number of genes controlled by CovR as revealed by transcription profile analysis: 2 genes are positively regulated, and 193 are repressed, including many that encode known or putative virulence factors. These findings suggested that CovR is a global repressor in virulence regulation of STSS-causing S. suis serotype 2.
