Growth media-dependent suppression of Candida albicans hyphal development by purpurin

Abstract

OBJECTIVES: To investigate the effect of growth media on the inhibitory activity of purpurin on hyphal growth in Candida albicans. METHODS: Four growth media that promote hyphal growth in Candida albicans SC5314 were used in this study. They were (A) RPMI medium containing 10% fetal bovine serum (FBS); (B) YPD medium containing 10% FBS; (C) Spider medium; and (D) Lee's medium. The inhibitory activity on hyphal development by purpurin in C. albicans SC5314 in these growth media was evaluated by incubating a standard fungal cell suspension (106 cells/mL) in each growth medium containing different concentrations of purpurin. Aliquots of the fungal cells were visualized by differential interference contrast microscopy after 16 h of incubation with agitation (250 rpm) at 37oC. Quantitative reverse transcription-PCR (qRT-PCR) was used to evaluate the expression of hyphal-specific genes and genes controlling amino acid metabolism in C. albicans SC5314. RESULTS: Inhibition of hyphal development by purpurin was dependent on the composition of the growth media. Purpurin abrogated hyphal growth in Lee's medium and RPMI medium containing 10% FBS; however, normal filamentation was evident in Spider medium and YPD medium containing 10% FBS. qRT-PCR analyses indicated that purpurin downregulated the expression of hyphal-specific genes and metabolic genes PDB1, KGD2, MDH1, and ILV5. CONCLUSIONS: Purpurin suppresses hyphal development in C. albicans SC5314 in a growth media-dependent manner. We envisage that the inhibition of hyphal growth is related to perturbation of metabolic pathways related to nutrient metabolism as filamentation is not observed in media containing amino acids and growth factors (i.e. Lee's medium and RPMI medium containing 10% FBS).