title: Candida-streptococcal mucosal biofilms display distinct structural and virulence characteristics depending on growth conditions and hyphal morphotypes.
abstract: Candida albicans and streptococci of the mitis group form communities in multiple oral sites, where moisture and nutrient availability can change spatially or temporally. This study evaluated structural and virulence characteristics of Candida-streptococcal biofilms formed on moist or semidry mucosal surfaces, and tested the effects of nutrient availability and hyphal morphotype on dual-species biofilms. Three-dimensional models of the oral mucosa formed by immortalized keratinocytes on a fibroblast-embedded collagenous matrix were used. Infections were carried out using Streptococcus oralis strain 34, in combination with a C. albicans wild-type strain, or pseudohyphal-forming mutant strains. Increased moisture promoted a homogeneous surface biofilm by C. albicans. Dual biofilms had a stratified structure, with streptococci growing in close contact with the mucosa and fungi growing on the bacterial surface. Under semidry conditions, Candida formed localized foci of dense growth, which promoted focal growth of streptococci in mixed biofilms. Candida biofilm biovolume was greater under moist conditions, albeit with minimal tissue invasion, compared with semidry conditions. Supplementing the infection medium with nutrients under semidry conditions intensified growth, biofilm biovolume and tissue invasion/damage, without changing biofilm structure. Under these conditions, the pseudohyphal mutants and S. oralis formed defective superficial biofilms, with most bacteria in contact with the epithelial surface, below a pseudohyphal mass, resembling biofilms growing in a moist environment. The presence of S. oralis promoted fungal invasion and tissue damage under all conditions. We conclude that moisture, nutrient availability, hyphal morphotype and the presence of commensal bacteria influence the architecture and virulence characteristics of mucosal fungal biofilms.
authors.affiliation: Division of Periodontology, School of Dental Medicine, University of Connecticut, Farmington, CT, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Bertolini
authors.affiliation: Division of Periodontology, School of Dental Medicine, University of Connecticut, Farmington, CT, USA.
authors.forename: H
authors.initials: H
authors.lastname: Xu
authors.affiliation: Division of Periodontology, School of Dental Medicine, University of Connecticut, Farmington, CT, USA.
authors.forename: T
authors.initials: T
authors.lastname: Sobue
authors.affiliation: School of Natural Sciences, University of California, Merced, CA, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Nobile
authors.affiliation: Division of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil.
authors.forename: A A
authors.initials: AA
authors.lastname: Del Bel Cury
authors.affiliation: Division of Periodontology, School of Dental Medicine, University of Connecticut, Farmington, CT, USA.
authors.forename: A
authors.initials: A
authors.lastname: Dongari-Bagtzoglou
mesh_terms: D018441:Biofilms / Q000145:classification / Q000254:growth & development; D002175:Candida; D002176:Candida albicans / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D003470:Culture Media; D025301:Hyphae / Q000145:classification / Q000254:growth & development; D009061:Mouth Mucosa / Q000382:microbiology* / Q000648:ultrastructure; D009154:Mutation; D019533:Streptococcus oralis / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D013559:Symbiosis; D014774:Virulence
chemical_list: D003470:Culture Media
keywords: Candida; Streptococcus; biofilms; infection models