title: SigB is a dominant regulator of virulence in Staphylococcus aureus small-colony variants.
abstract: Staphylococcus aureus small-colony variants (SCVs) are persistent pathogenic bacteria characterized by slow growth and, for many of these strains, an increased ability to form biofilms and to persist within host cells. The virulence-associated gene expression profile of SCVs clearly differs from that of prototypical strains and is often influenced by SigB rather than by the agr system. One objective of this work was to confirm the role of SigB in the control of the expression of virulence factors involved in biofilm formation and intracellular persistence of SCVs. This study shows that extracellular proteins are involved in the formation of biofilm by three SCV strains, which, additionally, have a low biofilm-dispersing activity. It was determined that SigB activity modulates biofilm formation by strain SCV CF07-S and is dominant over that of the agr system without being solely responsible for the repression of proteolytic activity. On the other hand, the expression of fnbA and the control of nuclease activity contributed to the SigB-dependent formation of biofilm of this SCV strain. SigB was also required for the replication of CF07-S within epithelial cells and may be involved in the colonization of lungs by SCVs in a mouse infection model. This study methodically investigated SigB activity and associated mechanisms in the various aspects of SCV pathogenesis. Results confirm that SigB activity importantly influences the production of virulence factors, biofilm formation and intracellular persistence for some clinical SCV strains.
authors.affiliation: Centre d'étude et de valorisation de la diversité microbienne, Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Mitchell
authors.forename: Alexandre
authors.initials: A
authors.lastname: Fugère
authors.forename: Karine
authors.initials: K
authors.lastname: Pépin Gaudreau
authors.forename: Eric
authors.initials: E
authors.lastname: Brouillette
authors.forename: Eric H
authors.initials: EH
authors.lastname: Frost
authors.forename: André M
authors.initials: AM
authors.lastname: Cantin
authors.forename: François
authors.initials: F
authors.lastname: Malouin
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D002460:Cell Line; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D005110:Extracellular Space / Q000378:metabolism; D006461:Hemolysis; D006801:Humans; D042541:Intracellular Space / Q000382:microbiology; D008168:Lung / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D051379:Mice; D059748:Proteolysis; D012141:Respiratory Tract Infections / Q000382:microbiology / Q000473:pathology; D012756:Sheep; D012808:Sigma Factor / Q000378:metabolism*; D013203:Staphylococcal Infections / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D013211:Staphylococcus aureus / Q000254:growth & development* / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D003851:Deoxyribonucleases