cDNA Microarray Analysis of Differential Gene Expression in Candida albicans Biofilm Exposed to Farnesol

Abstract

Candida albicans biofilms are structured microbial communities with high levels of drug resistance. Farnesol, a quorum-sensing molecule that inhibits hyphal formation in C. albicans, has been found to prevent biofilm formation by C. albicans. There is limited information, however, about the molecular mechanism of farnesol against biofilm formation. We used cDNA microarray analysis to identify the changes in the gene expression profile of a C. albicans biofilm inhibited by farnesol. Confocal scanning laser microscopy was used to visualize and confirm normal and farnesol-inhibited biofilms. A total of 274 genes were identified as responsive, with 104 genes up-regulated and 170 genes down-regulated. Independent reverse transcription-PCR analysis was used to confirm the important changes detected by microarray analysis. In addition to hyphal formation-associated genes (e.g., TUP1, CRK1, and PDE2), a number of other genes with roles related to drug resistance (e.g., FCR1 and PDR16), cell wall maintenance (e.g., CHT2 and CHT3), and iron transport (e.g., FTR2) were responsive, as were several genes encoding heat shock proteins (e.g., HSP70, HSP90, HSP104, CaMSI3, and SSA2). Further study of these differentially regulated genes is warranted to evaluate how they may be involved in C. albicans biofilm formation. Consistent with the down-regulation of the cell surface hydrophobicity-associated gene (CSH1), the water-hydrocarbon two-phase assay showed a decrease in cell surface hydrophobicity in the farnesol-treated group compared to that in the control group. Our data provide new insight into the molecular mechanism of farnesol against C. albicans biofilm formation.Candida albicans is a pleiomorphic fungus that can exist as either a commensal or an opportunistic pathogen and is capable of causing superficial to life-threatening infections. Predisposing factors for C. albicans infections include immunosuppressive therapy, antibiotic therapy, human immunodeficiency virus infection, diabetes, and old age. In addition, structured microbial communities attached to surfaces, commonly referred to as biofilms (29), have increasingly been found to be the sources of C. albicans infections. Biomaterials such as stents, shunts, prostheses (voice, heart valve, and knee prostheses), implants (lens and breast implants and dentures), endotracheal tubes, pacemakers, and various types of catheters have all been shown to facilitate C. albicans colonization and biofilm formation (1,20,27,28). It is estimated that biofilms might be involved in 65% of infections (30).Biofilms are spatially organized heterogeneous communities of cells embedded within an extrapolymeric matrix. In comparison with planktonic cells, biofilm cells display unique phenotypic traits (10, 11), the most outstanding of which is that they are notoriously resistant to both antimicrobial agents and host immune factors. Biofilm-associated infections are therefore difficult to treat because of their decreased susceptibilities to antimicrobial therapy. It is reported that C. alb...

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