title: Metal-dependent repression of siderophore and biofilm formation in Actinomyces naeslundii.
abstract: Actinomyces naeslundii is a pioneer of the oral cavity and forms a biofilm on the tooth's surface. Most bacteria require iron for survival and in pathogenic bacteria iron availability regulates virulence gene expression. Metal-dependent repressors control gene expression involved in metal transport and uptake including siderophores. Siderophores are small molecules synthesized by bacteria and fungi to acquire iron. The A. naeslundii genome was searched for a gene encoding a metal-dependent repressor. Actinomyces metal-dependent repressor or amdR was identified. The AmdR protein was examined for its ability to bind to the promoter sequence of a gene encoding the siderophore uptake (sid gene). According to gel shift assays, AmdR binds to the sid gene promoter sequences. In the authors' model, when iron is available AmdR binds to the sid promoter and represses sid gene expression. To further explore the role of AmdR, an amdR-defective strain of A. naeslundii was constructed and biofilm formation and siderophore production were evaluated. When iron is removed from the medium A. naeslundii increases biofilm and siderophore production. However, amdR-defective A. naeslundii is less sensitive to metal ion concentrations in the growth medium.
authors.affiliation: Department of Biology, Ripon College, Ripon, WI, USA.
authors.forename: Cas
authors.initials: C
authors.lastname: Moelling
authors.forename: Ross
authors.initials: R
authors.lastname: Oberschlacke
authors.forename: Price
authors.initials: P
authors.lastname: Ward
authors.forename: John
authors.initials: J
authors.lastname: Karijolich
authors.forename: Ksenia
authors.initials: K
authors.lastname: Borisova
authors.forename: Nikola
authors.initials: N
authors.lastname: Bjelos
authors.forename: Lori
authors.initials: L
authors.lastname: Bergeron
mesh_terms: D000190:Actinomyces / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007501:Iron / Q000378:metabolism / Q000494:pharmacology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D017262:Siderophores / Q000096:biosynthesis*