Ultrastructural architecture of colonies of different morphologies produced by phenotypic switching of a clinical strain of Candida tropicalis and biofilm formation by variant phenotypes

• Published in: Micron (Oxford, England : 1993) Vol. 42; no. 7; pp. 726 - 732
• Main Authors: França, Emanuele J.G., Andrade, Célia G.T.J., Furlaneto-Maia, Luciana, Serpa, Rosana, Oliveira, Marcelo T., Quesada, Regina M.B., Furlaneto, Marcia C.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2011
• Subjects: agar; Architecture; Biofilm; Biofilms; Biofilms - growth & development; Candida; Candida albicans - growth & development; Candida albicans - ultrastructure; Candida tropicalis; Candida tropicalis - growth & development; Candida tropicalis - ultrastructure; Cell Adhesion; Colonies; Colony Count, Microbial; Depression; Extracellular material; Microscopy, Electron, Scanning; Phenotype; scanning electron microscopy; Strain; Switches; Switching; yeasts; Biofilm; Candida tropicalis; Switching; Extracellular material
• DOI: 10.1016/j.micron.2011.03.008
• ISSN: 0968-4328; 1878-4291

► We investigated switching event in a Candida tropicalis clinical strain. ► The ultrastructural architecture of different phenotypes and biofilm were characterized. ► The biofilm-forming ability varied among the switch phenotypes. ► First time SEM was used to verify the architecture of whole Candida colonies at ultrastructural level. ► Extracellular material was correlated with complex colony architecture. Candida tropicalis has been identified as one of the most prevalent pathogenic yeast species of the Candida-non- albicans (CNA) group. Study of switching in C. tropicalis has not been the subject of extensive research. Therefore, we investigated switching event and characterized the ultrastructural architecture of different phenotypes and biofilm produced in a C. tropicalis clinical strain. Cells switched heritably, reversibly, and at a high frequency between four phenotypes readily distinguishable by the shape of colonies formed on agar at 25 °C. SEM analysis was used to verify the architecture of whole Candida colonies at ultrastructural level. The smooth phenotype (parental phenotype) colony showed a hemispherical shape character, while the semi-smooth was characterized by the presence of shallow marginal depressions. The ring and rough phenotypes exhibited more complex architecture and were characterized by the presence of deep central and peripheral depressions areas. The biofilm-forming ability varied among the switch phenotypes. After 12 h incubation, the smooth phenotype formed less biofilm compared to the other phenotypes ( P < 0.05). The electron microscopy analysis revealed that filamentation (pseudohyphae) was associated with ring and rough colonies. The ultrastructural analysis allowed the observation of the arrangement of individual cells within the colonies. At the deep central and peripheral depressions areas of the ring and rough colonies extracellular material was seen in different arrangements. The data presented here open new avenues to study a possible role for extracellular material in the formation and maintenance of the architecture of switch phenotypes in C. tropicalis. It is therefore essential that more strains be investigated to determine the biological significance of extracellular material in C. tropicalis phenotypic switching phenomenon.