Production of a Fungistatic Substance by Pseudallescheria boydii Isolated from Soil Amended with Vegetable Tissues and Its Significance

Department of Plant Pathology, National Chung Hsing University, Taichung, Taiwan.
Mycopathologia (Impact Factor: 1.53). 09/2009; 169(2):125-31. DOI: 10.1007/s11046-009-9237-1
Source: PubMed


Four fungal isolates that were able to use vegetable tissues for multiplication in soil were isolated and identified as Pseudallescheria boydii based on morphological characteristics and ITS sequence similarity. When grown in broth prepared from the same vegetable tissues used in soil amendment, all these isolates of P. boydii produced a substance capable of reducing the disease incidence of black leaf spot of spoon cabbage caused by Alternaria brassicicola and inhibiting the germination of A. brassicicola conidia. The substance, which was fungistatic, was very stable under high temperature and high or low pH value. It was soluble in polar solvents and insoluble in non-polar solvents. Molecular weight estimation and ion exchange ability tests suggest that the fungistatic compound has a molecular weight between 500 and 1,000 and has no charge on its molecule. Results from this study suggest the possession of a strong competitive saprophytic ability by P. boydii, which in turn may explain the widespread occurrence of this human pathogen in soil. Production of a fungistatic substance when P. boydii was grown in broth prepared from vegetable tissues suggests the importance of antibiotic production in its competitive saprophytic colonization of organic matters in soil.

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    • "As a matter of fact, both ergosterol and 18:2ω6,9 concentrations in 30-d-old PA microcosms were significantly lower than those found in coeval amended incubation control . This might be concomitantly due to both the limited growth of the inoculant and to the widely known ability of Pseudoallescheria spp. to produce fungistatic substances which also hampered the growth of resident fungi (Ko et al., 2010). On the one hand, and with regard to the impact of Pseudoallescheria sp. on bacterial biota, the absence of significant differences in densities of cultivable heterotrophic and hydrocarbonoclastic bacteria with the non-inoculated and amended incubation control, suggested that the augmented fungus did not negatively affect the bacterial biota. "
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    Full-text · Article · Feb 2015 · Science of The Total Environment
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    • "To study the ability of different adsorptive materials to remove the resistance-activating substances from the mycelium extract, Diaion SK1B cation exchange resins (equivalent to Amberlite 1R-120), Diaion SA 12A anion exchange resins (equivalent to Amberlite 1RA-420) and activated charcoal (Sigma–Aldrich, St. Louis, MO, USA) were washed as previously described to remove possible inhibitory substances (Ko et al., 2010b). An aliquot of 10 ml extract was shaken with 1 g cation exchange resins, anion exchange resins or activated charcoal in a 150-ml flask on a shaker for 24 h and filtered through a Whatman no. 1 filter paper. "
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    ABSTRACT: Microorganisms capable of utilizing vegetable tissues for multiplication in soil were isolated, cultivated in liquid medium prepared from the same vegetable tissues, and tested for ability to activate resistance in pepper leaves against Phytophthora blight caused by Phytophthora capsici. Among the 121 microorganisms isolated, a fungus Humicola phialophoroides showed distinct ability to produce substances capable of activating resistance. The resistance-activating substances produced by H. phialophoroides were mostly retained in the mycelium, and were readily extracted from the mycelium powder with polar solvents. The extract was not inhibitory to zoospore germination or germ tube growth of P. capsici. In pepper leaves, the extract took only about 12 h to activate resistance against P. capsici. After activation, washing treated leaf surface with water did not have much effect on the resistance expression. In addition to being able to move from the upper leaf surface to lower leaf surface, the resistance-activating substances were capable of moving 5 mm acropetally and 10 mm basipetally in pepper leaves, Chromatography of the extract on silica gel column suggests that there are probably more than three components in the extract with resistance-activating ability. The resistance-activating activity of the mycelium extract was not affected by treatment with either cation or anion exchange resins, indicating that none of the active components have positive or negative charges on their molecules. Results show that H. phialophoroides is capable of producing multiple resistance-activating substances which are mostly retained in the mycelium. The study also indicates that none of the active components have positive or negative charges on their molecules.
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