Temporal Analysis of Candida albicans Gene Expression During Biofilm Development: Phase-Dependent Cellular Activities

Candida albicans can form biofilm on the surface of indwelling medical devices. Biofilm formation is an importanat clinical problem because biofilm-grown cells have decreased susceptibility to antifungal agents. Microarray technology was used to identify changes in gene expression during biofilm development. Two biofilm substrates (denture and catheter) were used, with two C. albicans strains tested on each substrate. Three phases of biofilm development were studies: early (6 h), intermediate (12 h), and mature (48 h). Planktonic specimens were collected at the same time points. Comparison between biofilm and planktonic cell transcriptional profiles at each time point showed differential expression of approximately 3% of the genome in biofilm. Fewer than half of these genes were up-regulated in biofilm, compared to planktonic cells. Transcriptional profiles were also analyzed over the time course of biofilm development. Genes up-regulated during the early phase (6 h) primarily were involved in glycolytic and non-glycolytic carbohydrate assimilation, and amino acid metabolism. The largest number of differentially expressed genes were identified at the intermediate phase (12 h) of biofilm development where the largest increase in biofilm biomass occurs. Genes up-regulated at 12 h were involved in transcription, protein synthesis/translation, energy generation, cellular transport, and nucleotide metabolism. At mature phase (48 h), few genes were up-regulated compared to the 12 h time point. These data define phase-dependent changes in gene expression that occur during biofilm development and show how genes belong to different, but interconnected, functional categories regulate the morphology and phenotype of C. albicans biofilm Keywords: phase-dependent gene expression; comparative genomic hybridization; cell type comparison Two independent biological replicates were used in the microarray hybridization analysis. The experimental design of the array hybridizations was a 4-block (one for each strain and surface combination), simple loop (daisy-chain) design with a dye swap.