Abstract In contrast to yeast biofilms, those of filamentous fungi are relatively poorly understood, in particular with respect to their regulation. Cunninghamella elegans is a filamentous fungus that is of biotechnological interest as it catabolises drugs and other xenobiotics in an analogous manner to animals; furthermore, it can grow as a biofilm enabling repeated batch biotransformations. Precisely how the fungus switches from planktonic to biofilm growth is unknown and the aim of this study was to shed light on the possible mechanism of biofilm regulation. In dimorphic yeasts, alcohols such as tyrosol and 2-phenylethanol are known to control the yeast-to-hypha switch, and a similar molecule might be involved in regulating biofilm in C. elegans. Gas chromatography-mass spectrometry analysis of crude ethyl acetate extracts from supernatants of 72 h planktonic and biofilm cultures revealed 3-hydroxytyrosol as a prominent metabolite. Further quantification revealed that the amounts of the compound in planktonic cultures were substantially higher (>10-fold) than in biofilm cultures. In the presence of exogenous 3-hydroxytyrosol the growth of aerial mycelium was inhibited, and there was selective inhibition of biofilm when it was added to culture medium. There was no biotransformation of the compound when it was added to 72 h-old cultures, in contrast to the related compounds tyrosol and 2-phenylethanol, which were oxidised to a number of products. Therefore, we propose that 3-hydroxytyrosol is a new signalling molecule in fungi, which regulates biofilm growth.

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3-羟基酪醇调节线虫生物膜的生长

摘要与酵母生物膜相比，对丝状真菌的了解相对较少，特别是在它们的调节方面。Cunninghamella elegans 是一种具有生物技术意义的丝状真菌，因为它以类似于动物的方式分解代谢药物和其他异生物质；此外，它可以作为生物膜生长，从而实现重复的批量生物转化。确切地说，真菌如何从浮游生物转变为生物膜生长尚不清楚，本研究的目的是阐明生物膜调节的可能机制。在双态酵母中，已知酪醇和 2-苯基乙醇等醇类可以控制酵母菌到菌丝的转换，并且类似的分子可能参与调节秀丽隐杆线虫的生物膜。对 72 小时浮游生物和生物膜培养物上清液中粗乙酸乙酯提取物的气相色谱-质谱分析显示，3-羟基酪醇是一种重要的代谢物。进一步的量化显示，浮游培养物中化合物的量比生物膜培养物中的含量高得多（> 10 倍）。在外源性3-羟基酪醇存在下，气生菌丝体的生长受到抑制，加入培养基时对生物膜有选择性抑制作用。与相关化合物酪醇和 2-苯基乙醇相比，当将其添加到 72 小时的培养物中时，该化合物没有发生生物转化，它们被氧化成多种产物。因此，我们提出 3-羟基酪醇是真菌中一种新的信号分子，可调节生物膜的生长。