Enzymatic studies of the extracellular mucilage of two aquatic hyphomycetes,Lemonniera aquatica andMycocentrospora filiformis |
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Authors: | D. W. T. Au E. B. G. Jones S. T. Moss I. J. Hodgkiss |
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Affiliation: | (1) Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Ave., Kowloon, Hong Kong;(2) School of Biological Sciences, King Henry Building, University of Portsmouth, PO1 2DY Portsmouth, UK;(3) Department of Ecology and Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong |
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Abstract: | The effect of three carbohydrate-digesting enzymes, β-glucuronidase, lyticase and α-mannosidase and three proteolytic enzymes, α-chymotrypsin, papain and pronase E, on the strength of conidial attachment ofLemonniera aquatica andMycoentrospora filiformis was determined using the LH_Fowler cell Adhesion Measurement Module. Carbohydrate-digesting enzyme treatments showed significant differences in number of attached and detached, conidia versus control samples; little or no effect was observed for the proteolytic enzymes. Scanning and transmission electron microscopy showed different degrees of mucilage digestion by the carbohydrate-digesting enzymes on the germ hyphae, hyphae subtending appressoria, and appressoria of the two species. The loss of mucilage integrity and decrease in mucilage thickness were more pronounced on the hyphal sheaths than on the appressorial sheaths. Lyticase caused the most severe damage to the mucilage and cytoplasm of both fungi, particularlyL. aquatica. β-Glucuronidase and α-mannosidase exhibited more effective mucilage digestion onM. filiformis than onL. aquatica. Results indicate that the mucilage of the two species is mainly polysaccharide, containing more β-1,3-glucans than β-glucuronide and α-mannosyl residues. Variability of mucilage composition exists between these species and also between different structures of the same fungus. |
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Keywords: | appressorium aquatic hyphomycetes mucilage composition strength of attachment ultrastructure |
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