| Summary: | 碩士 === 國立臺灣大學 === 生化科技學系 === 105 === Candida tropicalis is an opportunistic human fungal pathogen that can cause mucosal infections and life-threatening candidemia. To adapt to different environmental niches, C. tropicalis could switch between yeast, true hyphae and pseudohyphae. Hyphae not only help the invasion to host cells, but also play critical role in biofilm development, thereby hampering antifungal drug treatment and recurrence. Previous report showed that six transcription factors, including Bcr1, Brg1, Efg1, Ndt80, Rob1, and Tec1, form a core transcriptional circuit to control biofilms. Thus, the aim of this study is to investigate the six C. tropicalis homologous transcriptional genes in regulation of hyphae formation and biofilm development. Under serum induction, the wildtype stran MYA 3404 (> 20%) forms filaments while wildtype strain ATCC 34139 (< 1%) do not. Thus, the following experiments and mutant constuctions will use the reference strain MYA 3404. Comparison with the wildtype strain, mutant strains of each gene caused a significant reduction in biofilms (WT: 5.16 mg; bcr1∆: 0.50 mg; brg1∆: 2.58 mg; efg1∆: 0.02 mg; ndt80∆: 0.42 mg; rob1∆: 3.45 mg; tec1∆: 2.51 mg). During the response to bovine serum, hyphal formation between each mutant and the wildtype strain also resulted in significant difference (YL477: 39.17%; bcr1∆: 23.54%; brg1∆: 18.49%; efg1∆: 0.53%; ndt80∆: 60.53%; rob1∆: 28.59%; tec1∆: 11.06%). Interestingly, hyphae in the C. tropicalis ndt80∆ highly increased. Under Spider-Glu culture condition, similar results were observed, except rob1∆ in which it showed comparable filamentation percentages to those of the wildtype strain (YL477: 4.23%; bcr1∆: 0.86%; brg1∆: 0.88%; efg1∆: 1.89%; ndt80∆: 24.41%; rob1∆: 7.29%; tec1∆: 1.41%). These data suggest that Bcr1, Brg1, Efg1, Ndt80, Rob1 and Tec1 in C. tropicalis play conserved roles in biofilm formation. However, different to the C. albicans Ndt80, Ndt80 in C. tropicalis negatively regulates hyphal formation.
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