Wösten H A, van Wetter M A, Lugones L G, van der Mei H C, Busscher H J, Wessels J G
Groningen Biomolecular Sciences, Biotechnology Institute, Laboratory of Molecular Plant Biology, Department of Microbiology, University of Groningen, Kerklaan 30 9751, NN Haren, The Netherlands. wostenha@biol rug.nl.
Curr Biol. 1999 Jan 28;9(2):85-8. doi: 10.1016/s0960-9822(99)80019-0.
Fungi are well known to the casual observer for producing water-repelling aerial moulds and elaborate fruiting bodies such as mushrooms and polypores. Filamentous fungi colonize moist substrates (such as wood) and have to breach the water-air interface to grow into the air. Animals and plants breach this interface by mechanical force. Here, we show that a filamentous fungus such as Schizophyllum commune first has to reduce the water surface tension before its hyphae can escape the aqueous phase to form aerial structures such as aerial hyphae or fruiting bodies. The large drop in surface tension (from 72 to 24 mJ m-2) results from self-assembly of a secreted hydrophobin (SC3) into a stable amphipathic protein film at the water-air interface. Other, but not all, surface-active molecules (that is, other class I hydrophobins and streptofactin from Streptomyces tendae) can substitute for SC3 in the medium. This demonstrates that hydrophobins not only have a function at the hyphal surface but also at the medium-air interface, which explains why fungi secrete large amounts of hydrophobin into their aqueous surroundings.
对于普通观察者来说，真菌因能产生防水的气生霉菌以及如蘑菇和多孔菌等精致的子实体而广为人知。丝状真菌在潮湿的基质（如木材）上定殖，并且必须突破水 - 空气界面才能向空气中生长。动物和植物通过机械力突破这个界面。在这里，我们表明，像裂褶菌这样的丝状真菌在其菌丝能够逃离水相以形成气生结构（如气生菌丝或子实体）之前，首先必须降低水的表面张力。表面张力的大幅下降（从72降至24 mJ m-2）是由于一种分泌的疏水蛋白（SC3）在水 - 空气界面自组装成稳定的两亲性蛋白膜所致。其他但并非所有的表面活性分子（即其他I类疏水蛋白和来自天蓝色链霉菌的链霉肌动蛋白）可以在培养基中替代SC3。这表明疏水蛋白不仅在菌丝表面起作用，而且在培养基 - 空气界面也起作用，这就解释了为什么真菌会向其周围的水环境中分泌大量的疏水蛋白。
