title: IsdC from Staphylococcus lugdunensis induces biofilm formation under low-iron growth conditions.
abstract: Staphylococcus lugdunensis is a coagulase-negative staphylococcus that is a commensal of humans and an opportunistic pathogen. It can cause a spectrum of infections, including those that are associated with the ability to form biofilm, such as occurs with endocarditis or indwelling medical devices. The genome sequences of two strains revealed the presence of orthologues of the ica genes that are responsible for synthesis of poly-N-acetylglucosamine (PNAG) that is commonly associated with biofilm in other staphylococci. However, we discovered that biofilm formed by a panel of S. lugdunensis isolates growing in iron-restricted medium was susceptible to degradation by proteases and not by metaperiodate, suggesting that the biofilm matrix comprised proteins and not PNAG. When the iron concentration was raised to 1 mM biofilm formation by all strains tested was greatly reduced. A mutant of strain N920143 lacking the entire locus that encodes iron-regulated surface determinant (Isd) proteins was defective in biofilm formation under iron-limited conditions. An IsdC-null mutant was defective, whereas IsdK, IsdJ, and IsdB mutants formed biofilm to the same level as the parental strain. Expression of IsdC was required both for the primary attachment to unconditioned polystyrene and for the accumulation phase of biofilm involving cell-cell interactions. Purified recombinant IsdC protein formed dimers in solution and Lactococcus lactis cells expressing only IsdC adhered to immobilized recombinant IsdC but not to IsdJ, IsdK, or IsdB. This is consistent with a specific homophilic interaction between IsdC molecules on neighboring cells contributing to accumulation of S. lugdunensis biofilm in vivo.
authors.affiliation: Department of Molecular Medicine, Unit of Biochemistry, Pavia, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Missineo
authors.forename: Antonella
authors.initials: A
authors.lastname: Di Poto
authors.forename: Joan A
authors.initials: JA
authors.lastname: Geoghegan
authors.forename: Simonetta
authors.initials: S
authors.lastname: Rindi
authors.forename: Simon
authors.initials: S
authors.lastname: Heilbronner
authors.forename: Valentina
authors.initials: V
authors.lastname: Gianotti
authors.forename: Carla Renata
authors.initials: CR
authors.lastname: Arciola
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Foster
authors.forename: Pietro
authors.initials: P
authors.lastname: Speziale
authors.forename: Giampiero
authors.initials: G
authors.lastname: Pietrocola
mesh_terms: D000704:Analysis of Variance; D001422:Bacterial Adhesion / Q000502:physiology; D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D003470:Culture Media / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007501:Iron / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013203:Staphylococcal Infections / Q000382:microbiology*; D057787:Staphylococcus lugdunensis / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D003470:Culture Media; D011994:Recombinant Proteins; D007501:Iron