Strain JAU4234, identified as Streptomyces padanus, was isolated from soil collected in Jiangxi Province, China. It produced actinomycin X2, fungichromin, and a new polyene macrolide compound with antifungal activity, antifungalmycin 702. Antifungalmycin 702 had good general antifungal activity and may have potential future agricultural and/or clinical applications.
Antifungalmycin 702, a novel polyene macrolide antibiotic produced by Streptomyces padanus JAU4234, strongly inhibited mycelial growth of the rice blast fungus, Magnaporthe grisea, with EC50 of 37 μg/ml and EC90 of 136 μg/ml. Significant reduction in the number of conidia was observed at above 20 μg/ml. Conidia germination and appressorium formation were also suppressed and were not viable with >40 μg/ml. When treated with antifungalmycin 702, hyphae morphology became irregular. Based on microscopic examination, antifungalmycin 702 may exert its antifungal activity by changing the structure of cell membranes and the cytoskeleton and interacting with the organelles. Antifungalmycin 702 thus has potential as a new fungicide in the treatment of rice blast disease.
Antifungalmycin 702, a new polyene macrolide antibiotic produced by
Streptomyces
padanus
JAU4234, has a broad antifungal activity and may have potential future agricultural and/or clinical applications. However, the mechanism of antifungal action of antifungalmycin 702 remains unknown. Antifungalmycin 702 strongly inhibited mycelial growth and sclerotia formation/germination of Rhizoctonia solani. When treated with antifungalmycin 702, the hyphae morphology of
R
. solani
became more irregular. The membrane and the cellular organelles were disrupted and there were many vacuoles in the cellular space. The lesion in the plasma membrane was detected through the increase of membrane permeability, lipid peroxidation and leakage of cell constituents. In summary, antifungalmycin 702 may exert its antifungal activity against
R
. solani
by changing the structure of cell membranes and the cytoskeleton and interacting with the organelles.
BACKGROUND: Fermentation of the industrial vitamin B 12 by Pseudomonas denitrificans usually utilizes sucrose or maltose as the sole carbon source, which results in increased medium costs. In order to decrease the fermentation cost, it is crucial and essential to employ a low-cost and convenient raw material as an alternative medium substrate for industrial vitamin B 12 production.
RESULTS:The results obtained in chemically defined medium showed that glutamate and sucrose were favorable for cell growth and vitamin B 12 biosynthesis of P. denitrificans. Due to containing a mass of ingredients such as sucrose, glutamate and betaine, beet molasses was consequently chosen as the main medium substrate for industrial P. denitrificans fermentation in a 120 000 L fermenter. Vitamin B 12 production reached 181.75 mg L -1 . CONCLUSIONS: Beet molasses is a by-product of the sugar industry and is thus very inexpensive, and it was proved that beet molasses was an efficient and economical medium substrate for industiral vitamin B 12 fermentation by P. denitrificans.
These authors contributed equally to this work. (2) were isolated from the culture mycelia of Streptomyces padanus 702 via bioactivity-guided fractionation using various chromatographic procedures. Their structures were elucidated on the basis of spectral analysis, and 1 is a new polyene macrolide.
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