A novel method for identifying hydrophobicity on fungal surfaces Henry Wai CHAU a , Bing Cheng SI a, *, Yit Kheng GOH b , Vladimir VUJANOVIC b a College of Agriculture and Bioresources, Department of Soil Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada b College of Agriculture and Bioresources, Department of Food & Bioproduct Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada article info Article history: Received 12 February 2009 Received in revised form 4 April 2009 Accepted 12 June 2009 Available online 30 June 2009 Corresponding Editor: Martin Grube Keywords: Chronoamphiphilic Contact angles Fungal surface properties Hydrophilic Hydrophobicity abstract Fungal surface hydrophobicity has many ecological functions and water contact angles measurement is a direct and simple approach for its characterization. The objective of this study was to evaluate if in-vitro growth conditions coupled with versatile image anal- ysis allows for more accurate fungal contact angle measurements. Fungal cultures were grown on agar slide media and contact angles were measured utilizing a modified micro- scope and digital camera setup. Advanced imaging software was adopted for contact angle determination. Contact angles were observed in hydrophobic, hydrophilic and a newly cre- ated chronoamphiphilic class containing fungi taxa with changing surface hydrophobicity. Previous methods are unable to detect slight changes in hydrophobicity, which provide vi- tal information of hydrophobicity expression patterns. Our method allows for easy and ef- ficient characterization of hydrophobicity, minimizing disturbance to cultures and quantifying subtle variation in hydrophobicity. ª 2009 The British Mycological Society. Published by Elsevier Ltd. All rights reserved. Introduction Microbial surface characteristics via the cell wall interactions have important implications in a variety of processes (Dague et al. 2007). It is one of the surface properties influencing mi- crobial interactions at the fungal interface (Van Loosdrecht et al. 1987; Gannon et al. 1991). Key functions include support- ing internal turgor pressure, appressorium formation in the cells and also providing structure, shape, adhesion and aggre- gation (Dague et al. 2007; Lee & Dean 1994). Microorganisms and their interactions at the interfaces are known to be con- trolled by physicochemical properties of the cellular surface (Smits et al. 2003). Research suggested that the presence of hy- drophobic moieties causes the fungal cell surface to exhibit hydrophobic properties (Hazen 1990; Hazen et al. 1990; Lopez-Ribot et al. 1991; De Vries et al. 1993). Spore dispersal, ad- hesion, pathogenesis and breaking surface tension have been linked to fungal hydrophobic moieties, which were identified as a class of cysteine rich proteins called hydrophobins (Bidochka et al. 1995a,b; Hazen 1990; Stringer et al. 1991; Wes- sels 1992; Wessels et al. 1991). The relationship between hydrophobins and fungal hydrophobicity is well understood (Wo ¨ sten & de Vocht 2000), but how the expression of these proteins affects contact angle measurement of fungal sur- faces has not been addressed. It is known that changes in the developmental stages of a fungus cause expression of dif- ferent hydrophobins, which is likely one of causes of change in fungal surface hydrophobicity (Pen ˜ as et al. 1998). Besides * Corresponding author. Tel.: þ1 306 966 6877; fax: þ1 306 966 6881. E-mail address: bing.si@usask.ca journal homepage: www.elsevier.com/locate/mycres mycological research 113 (2009) 1046–1052 0953-7562/$ – see front matter ª 2009 The British Mycological Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.mycres.2009.06.007