Enhanced biofilm formation by Candida tropicalis morphotypes under host-mimicking conditions: Insights into cell wall modifications and gene expression.

BACKGROUND AND

OBJECTIVE

Candida tropicalis is an important fungal pathogen capable of colonizing diverse host niches. This study investigates how phenotypic switching influences biofilm formation by C. tropicalis under host-mimicking conditions, including simulative vaginal secretions (VS) and artificial urine (AU).

METHODS

Our study analyzed three morphotypes derived from the 49.07 switching system: a clinical strain (parental) and two phenotypic switching morphotypes, rough variant and rough revertant (RR). Biofilm formation on polystyrene was assessed under different culture conditions (AU, VS, and RPMI-1640). Biofilm characteristics, including filamentation, cell surface hydrophobicity, and cell wall composition (β-glucan, chitin, and mannan), were investigated. Additionally, the expression levels of Agglutinin-like sequence genes (CtrALS1, CtrALS3) and the EFG1 gene (Enhanced filamentous growth protein 1) was quantified using RT-qPCR.

RESULTS

Phenotypic switching morphotypes of C. tropicalis produced significantly more biofilm under host-like conditions compared to the parental strain. Increased filamentation in the rough variant and revertant correlated with biofilm biomass across all conditions. Switched morphotypes also exhibited higher cell surface hydrophobicity and altered cell wall composition, with increased β-glucan and variable chitin content under host-mimicking conditions. The RR morphotype showed higher expression of CtrALS3 and EFG1 compared to the parental strain in AU and VS.

CONCLUSIONS

Phenotypic switching influences important biofilm traits-hydrophobicity, filamentation, cell wall composition, and gene expression-in host-mimicking environments. These findings highlight the role of phenotypic switching in C. tropicalis adaptation to host niches, particularly vaginal fluids and urine.