title: SdrC induces staphylococcal biofilm formation through a homophilic interaction.
abstract: The molecular pathogenesis of many Staphylococcus aureus infections involves growth of bacteria as biofilm. In addition to polysaccharide intercellular adhesin (PIA) and extracellular DNA, surface proteins appear to mediate the transition of bacteria from planktonic growth to sessile lifestyle as well as biofilm growth, and can enable these processes even in the absence of PIA expression. However, the molecular mechanisms by which surface proteins contribute to biofilm formation are incompletely understood. Here we demonstrate that self-association of the serine-aspartate repeat protein SdrC promotes both bacterial adherence to surfaces and biofilm formation. However, this homophilic interaction is not required for the attachment of bacteria to abiotic surfaces. We identified the subdomain that mediates SdrC dimerization and subsequent cell-cell interactions. In addition, we determined that two adjacently located amino acid sequences within this subdomain are required for the SdrC homophilic interaction. Comparative amino acid sequence analysis indicated that these binding sites are conserved. In summary, our study identifies SdrC as a novel molecular determinant in staphylococcal biofilm formation and describes the mechanism responsible for intercellular interactions. Furthermore, these findings contribute to a growing body of evidence suggesting that homophilic interactions between surface proteins present on neighbouring bacteria induce biofilm growth.
authors.affiliation: Center for Infectious & Inflammatory Diseases, Institute and Bioscience and Technology, Texas A&M Health Science Center, Houston, TX, USA; Department of Infectious Diseases, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA.
authors.forename: E Magda
authors.initials: EM
authors.lastname: Barbu
authors.forename: Chris
authors.initials: C
authors.lastname: Mackenzie
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Foster
authors.forename: Magnus
authors.initials: M
authors.lastname: Höök
mesh_terms: D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms; D019281:Dimerization; D006801:Humans; D008969:Molecular Sequence Data; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C118508:SdrC protein, Staphylococcus aureus