Analyzing the influence of FLO11 on Mat formation in clinical isolates of Saccharomyces cerevisiae in Taiwan
Date Issued
2009
Date
2009
Author(s)
Wong, Wai-Ian
Abstract
The first step of biofilm formation is surface attachment for microbes, and the consequence of biofilm formation is highly correlated to drug resistance. That is why many studies focus on how to prevent microbes’ adhesion and drug resistance. Saccharomyces cerevisiae cells form the initial structure of biofilm called mats which is dependent on FLO11gene. The previous studies on FLO11 have been focused on lab strain ∑1278b in two directions: the regulation of FLO11 and how the FLO11 phenotype is affected by its central tandem repeat. In this study, in order to find out the regulation of FLO11, first, mats phenotypes and the expression levels of FLO11 were compared in clinical isolates of S. cerevisiae with lab strain ∑1278b. Second, we wanted to find out the relationship between FLO11 genotypes and mats phenotypes. Third, we want to study about the relationship between mats formation and antifungal drug resistance. We found that one of our National Taiwan Hospital clinical isolates, named YYC1, could form typical mats phenotype. After further screening the mats phenotypes in YYC1 segregants from 15 tetrads, the result indicated that mats phenotype might be a quantitative trait. We also found a special phenotype called “hyper mats” in our study. In the 96-well adherence assay, we found that the adhesion ability of strains was positively related to mat formation. Nevertheless, this assay might not be sensitive enough to distinguish the differences between the typical mats phenotype and “hyper mats.” The results of Northern blot analysis showed that the expression of FLO11 in log phase cells is important for mat formation. However, the change of FLO11 expression levels does not seem to relate to different mats phenotypes. In order to analyze the different expression levels of FLO11 between YYC1 and ∑1278b, we sequenced 3.1 kb of the FLO11 promoter regions in both strains. However, we could not find out any significant change in FLO11 promoter of YYC1 compared to ∑1278b. On the other hand, we surprisingly found that the length of the tandem repeats in FLO11 coding regions in YYC1 was about 1 kb shorter than that in ∑1278b. These results indicated that the different mats phenotypes between YYC1 and ∑1278b might be due to the length of this tandem repeat sequences. In addition, we have screened the antifungal drug resistance on our S. cerevisiae clinical isolates. However, we could not find out the direct relationship between mat formation and antifungal drug resistance in S. cerevisiae. In conclusion, in our study, we found that mat formation is dependent on FLO11 expression, although higher expression levels of FLO11 did not seem to relate to “hyper mats” phenotype. Our data also inferred that central tandem repeat sequences of FLO11 perhaps affect mats phenotypes in strains we analyzed. We found that the antifungal drug resistance might not directly correlate with mats formation inS. cerevisiae.
Subjects
biofilm
antifungal drug susceptibility assay
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