Alem Mohammed A S, Oteef Mohammed D Y, Flowers T Hugh, Douglas L Julia
Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Eukaryot Cell. 2006 Oct;5(10):1770-9. doi: 10.1128/EC.00219-06. Epub 2006 Sep 15.
Tyrosol and farnesol are quorum-sensing molecules produced by Candida albicans which accelerate and block, respectively, the morphological transition from yeasts to hyphae. In this study, we have investigated the secretion of tyrosol by C. albicans and explored its likely role in biofilm development. Both planktonic (suspended) cells and biofilms of four C. albicans strains, including three mutants with defined defects in the Efg 1 and Cph 1 morphogenetic signaling pathways, synthesized extracellular tyrosol during growth at 37 degrees C. There was a correlation between tyrosol production and biomass for both cell types. However, biofilm cells secreted at least 50% more tyrosol than did planktonic cells when tyrosol production was related to cell dry weight. The addition of exogenous farnesol to a wild-type strain inhibited biofilm formation by up to 33% after 48 h. Exogenous tyrosol appeared to have no effect, but scanning electron microscopy revealed that tyrosol stimulated hypha production during the early stages (1 to 6 h) of biofilm development. Experiments involving the simultaneous addition of tyrosol and farnesol at different concentrations suggested that the action of farnesol was dominant, and 48-h biofilms formed in the presence of both compounds consisted almost entirely of yeast cells. When biofilm supernatants were tested for their abilities to inhibit or enhance germ tube formation by planktonic cells, the results indicated that tyrosol activity exceeds that of farnesol after 14 h, but not after 24 h, and that farnesol activity increases significantly during the later stages (48 to 72 h) of biofilm development. Overall, our results support the conclusion that tyrosol acts as a quorum-sensing molecule for biofilms as well as for planktonic cells and that its action is most significant during the early and intermediate stages of biofilm formation.
酪醇和法尼醇是白色念珠菌产生的群体感应分子，分别加速和阻断酵母到菌丝的形态转变。在本研究中，我们调查了白色念珠菌酪醇的分泌情况，并探讨了其在生物膜形成中的可能作用。包括三株在Efg 1和Cph 1形态发生信号通路中存在特定缺陷的突变株在内的四株白色念珠菌菌株的浮游（悬浮）细胞和生物膜在37℃生长期间均合成细胞外酪醇。两种细胞类型的酪醇产生量与生物量之间均存在相关性。然而，当酪醇产生量与细胞干重相关时，生物膜细胞分泌的酪醇比浮游细胞至少多50%。向野生型菌株添加外源性法尼醇48小时后，生物膜形成受到高达33%的抑制。外源性酪醇似乎没有影响，但扫描电子显微镜显示，酪醇在生物膜形成的早期阶段（1至6小时）刺激菌丝产生。涉及同时添加不同浓度酪醇和法尼醇的实验表明，法尼醇的作用占主导地位，在两种化合物存在的情况下形成的48小时生物膜几乎完全由酵母细胞组成。当测试生物膜上清液抑制或增强浮游细胞芽管形成的能力时,结果表明，14小时后酪醇活性超过法尼醇，但24小时后则不然，并且在生物膜形成的后期阶段（48至72小时）法尼醇活性显著增加。总体而言，我们的结果支持以下结论：酪醇作为生物膜以及浮游细胞的群体感应分子发挥作用，并且其作用在生物膜形成的早期和中期最为显著。
