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Int J Biol Sci 2008; 4(5):330-337. doi:10.7150/ijbs.4.330

Short Research Communication

Antifungal Potential of Extracellular Metabolites Produced by Streptomyces hygroscopicus against Phytopathogenic Fungi

Benjaphorn Prapagdee1 ✉, Chutima Kuekulvong1, Skorn Mongkolsuk2,3

1. Laboratory of Environmental Biotechnology, Faculty of Environment and Resource Studies, Mahidol University, Salaya, Nakhonpathom 73170, Thailand
2. Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
3. Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok 10210, Thailand.

Abstract

Indigenous actinomycetes isolated from rhizosphere soils were assessed for in vitro antagonism against Colletotrichum gloeosporioides and Sclerotium rolfsii. A potent antagonist against both plant pathogenic fungi, designated SRA14, was selected and identified as Streptomyces hygroscopicus. The strain SRA14 highly produced extracellular chitinase and β-1,3-glucanase during the exponential and late exponential phases, respectively. Culture filtrates collected from the exponential and stationary phases inhibited the growth of both the fungi tested, indicating that growth suppression was due to extracellular antifungal metabolites present in culture filtrates. The percentage of growth inhibition by the stationary culture filtrate was significantly higher than that of exponential culture filtrate. Morphological changes such as hyphal swelling and abnormal shapes were observed in fungi grown on potato dextrose agar that contained the culture filtrates. However, the antifungal activity of exponential culture filtrates against both the experimental fungi was significantly reduced after boiling or treatment with proteinase K. There was no significant decrease in the percentage of fungal growth inhibition by the stationary culture filtrate that was treated as above. These data indicated that the antifungal potential of the exponential culture filtrate was mainly due to the presence of extracellular chitinase enzyme, whereas the antifungal activity of the stationary culture filtrate involved the action of unknown thermostable antifungal compound(s).

Keywords: Antifungal metabolites, Streptomyces hygroscopicus, Phytopathogenic fungi, Cell-free culture filtrates

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How to cite this article:
Prapagdee B, Kuekulvong C, Mongkolsuk S. Antifungal Potential of Extracellular Metabolites Produced by Streptomyces hygroscopicus against Phytopathogenic Fungi. Int J Biol Sci 2008; 4(5):330-337. doi:10.7150/ijbs.4.330. Available from http://www.ijbs.com/v04p0330.htm