Mitogenic factor (MF) is the major DNase of serotype M89 Streptococcus pyogenes.
To investigate the role of mitogenic factor (MF) in streptococcal pathogenesis, the structural gene (mf) encoding this protein was disrupted in a clinical isolate of Streptococcus pyogenes H293, to yield the isogenic mutant H363. Growth in enriched broth and on blood agar was unaffected by disruption of mf. Cell-free broth supernatants from H293 and H363 demonstrated identical promitogenic activities when co-incubated with human peripheral blood mononuclear cells, even when diluted 100000-fold, showing that MF is not a major streptococcal mitogen compared with other secreted superantigens. Disruption of mf resulted in complete loss of DNase B production and detectable DNase activity in H363 compared with the parent strain, confirming that the single gene mf, which is present in all group A streptococcal M serotypes studied, encodes DNase B. Despite loss of DNase activity, the virulence of S. pyogenes in a mouse model of necrotizing fasciitis and myositis was unaffected.
Sriskandan
Shiranee
S
Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
Unnikrishnan
Meera
M
Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
Krausz
Thomas
T
Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
Cohen
Jonathan
J
Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D003851:Deoxyribonucleases / Q000235:genetics* / Q000502:physiology*; D019115:Fasciitis, Necrotizing / Q000209:etiology; D017353:Gene Deletion; D005798:Genes, Bacterial; D006801:Humans; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D051379:Mice; D008934:Mitogens / Q000235:genetics* / Q000502:physiology*; D009220:Myositis / Q000209:etiology; D010957:Plasmids / Q000235:genetics; D012703:Serotyping; D013290:Streptococcal Infections / Q000209:etiology / Q000276:immunology / Q000473:pathology; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D014170:Transformation, Genetic; D014774:Virulence / Q000235:genetics / Q000502:physiology
D001426:Bacterial Proteins; D017931:DNA Primers; D015850:Interleukin-6; D008934:Mitogens; C083356:mitogenic factor, Streptococcus; D003851:Deoxyribonucleases; C020069:deoxyribonuclease B