title: Role of Candida albicans secreted aspartyl protease Sap9 in interkingdom biofilm formation.
abstract: The fungus Candida albicans colonizes oral cavity surfaces and is carried by up to 60% of human populations. Biofilm development by C. albicans may be modulated by oral streptococci, such as Streptococcus gordonii, S. oralis or S. mutans, so as to augment pathogenicity. In this study we sought to determine if the cell wall-associated secreted aspartyl proteinase Sap9 was necessary for hyphal adhesin functions associated with biofilm community development. A sap9Δ mutant of C. albicans SC5314 formed biofilms that were flatter, and contained fewer blastospores and more hyphal filaments than the parent strain. This phenotypic difference was accentuated under flow (shear) conditions and in the presence of S. gordonii. Dual-species biofilms of C. albicans sap9Δ with S. oralis, S. sanguinis, S. parasanguinis, S. mutans and Enterococcus faecalis all contained more matted hyphae and more bacteria bound to substratum compared to C. albicans wild type. sap9Δ mutant hyphae showed significantly increased cell surface hydrophobicity, ∼25% increased levels of binding C. albicans cell wall protein Als3, and reduced interaction with Eap1, implicating Sap9 in fungal cell-cell recognition. These observations suggest that Sap9 is associated with protein-receptor interactions between fungal cells, and with interkingdom communication in the formation of polymicrobial biofilm communities.
authors.affiliation: School of Oral and Dental Sciences, University of Bristol, Bristol BS1 2LY, UK.
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Dutton
authors.affiliation: School of Oral and Dental Sciences, University of Bristol, Bristol BS1 2LY, UK howard.jenkinson@bristol.ac.uk.
authors.forename: Howard F
authors.initials: HF
authors.lastname: Jenkinson
authors.affiliation: Department of Oral Immunology and Infectious Diseases, University of Louisville, Louisville, KY 40202, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lamont
authors.affiliation: School of Oral and Dental Sciences, University of Bristol, Bristol BS1 2LY, UK.
authors.forename: Angela H
authors.initials: AH
authors.lastname: Nobbs
mesh_terms: D000328:Adult; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D002176:Candida albicans / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D013293:Enterococcus faecalis / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D025301:Hyphae / Q000378:metabolism; D056265:Microbial Interactions / Q000502:physiology; D018613:Microscopy, Confocal; D009055:Mouth / Q000382:microbiology; D054773:Streptococcus gordonii / Q000378:metabolism*; D013295:Streptococcus mutans / Q000378:metabolism*
chemical_list: C113620:ALS3 protein, Candida albicans; D005656:Fungal Proteins; D016282:Aspartic Acid Endopeptidases; C116371:Sap9 protein, Candida albicans
keywords: Microbial interactions; Streptococcus gordonii; Streptococcus mutans; mixed species communities; oral cavity biofilms