title: Metal ions may suppress or enhance cellular differentiation in Candida albicans and Candida tropicalis biofilms.
abstract: Candida albicans and Candida tropicalis are polymorphic fungi that develop antimicrobial-resistant biofilm communities that are characterized by multiple cell morphotypes. This study investigated cell type interconversion and drug and metal resistance as well as community organization in biofilms of these microorganisms that were exposed to metal ions. To study this, Candida biofilms were grown either in microtiter plates containing gradient arrays of metal ions or in the Calgary Biofilm Device for high-throughput susceptibility testing. Biofilm formation and antifungal resistance were evaluated by viable cell counts, tetrazolium salt reduction, light microscopy, and confocal laser scanning microscopy in conjunction with three-dimensional visualization. We discovered that subinhibitory concentrations of certain metal ions (CrO(4)(2-), Co(2+), Cu(2+), Ag(+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), AsO(2)(-), and SeO(3)(2-)) caused changes in biofilm structure by blocking or eliciting the transition between yeast and hyphal cell types. Four distinct biofilm community structure types were discerned from these data, which were designated "domed," "layer cake," "flat," and "mycelial." This study suggests that Candida biofilm populations may respond to metal ions to form cell-cell and solid-surface-attached assemblages with distinct patterns of cellular differentiation.
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Canada.
authors.forename: Joe J
authors.initials: JJ
authors.lastname: Harrison
authors.forename: Howard
authors.initials: H
authors.lastname: Ceri
authors.forename: Jerome
authors.initials: J
authors.lastname: Yerly
authors.forename: Maryam
authors.initials: M
authors.lastname: Rabiei
authors.forename: Yaoping
authors.initials: Y
authors.lastname: Hu
authors.forename: Robert
authors.initials: R
authors.lastname: Martinuzzi
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Turner
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D002176:Candida albicans / Q000187:drug effects / Q000254:growth & development*; D041022:Candida tropicalis / Q000187:drug effects / Q000254:growth & development*; D015169:Colony Count, Microbial; D003470:Culture Media; D007477:Ions / Q000494:pharmacology; D019216:Metals, Heavy / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D018613:Microscopy, Confocal
chemical_list: D000935:Antifungal Agents; D003470:Culture Media; D007477:Ions; D019216:Metals, Heavy