Studies On The Mechanism Of A New Antibiotic Wanlongmycin Against Phytophthora Melonis

Wanlongmycin, the peoperty right of which is owned by our nation, is one antibiotic that could effectively prevent and cure a wide type of oomyces causing plant diseases. It has a new type of molecular structure which owns two 2-carboxyl-quinoxaline chromophores,belonging to the depsipeptide. This dissertation elucidates its mechanism against plant pathogenic fungi Phytophthora melonis from the cellular, sub-cellular, molecular levels, and then classifies its producing strain GAAS 2507 .Based on the morphological, physiological and biochemical characteristics, the taxonomy and 16S rDNA sequence analysis of GAAS2507, it is sorted to a new subspecie belonging to Actinomycetales Streptomycetaceae Streptomyces Streptomyces griseovariabilis and named as Streptomyces griseovariabilis subsp. Bandungensis subsp. nov.. Its 16S rDNA sequence is stored in the Genbank.Combining with the characteristics of the Phytophthora melonis causing plant diseases, mechanism is discussed from the angle of plant pathology and micrology. It turns out that Wanlongmycin could not only restrain the growth of the mycelia, but also the formation of its swarm sporangium and swam spores, the germination of its dormant spores and their nosogenicity. What's more, wanlongmycin could kill its swam spores.The Phytophthora melonis restraining mechanism is explored in cellular level.After being treated by Wanlongmycin,the growth rate of its mycelia slows down distinctly. Under optical microscope,the mycelia became swelled and distorated, and the protoplast all agglutinate; Under SEM,after treating Phytophthora melonis mycelia with different concentrations of Wanglongmycin, they became inflated, blasted, wizened and distorted,the surface of the mycelia became rough,and the new born mycelium are all distorted; Under TEM, the transect are all obscure, the endocellular components become condensed and form vacant regions,but the shape of the mycelia are intact, neither holes nor breached appearing.After studying the leakage of the endocellular materials and the membrane osmosis of Phytophthora melonis mycelia and spores treated by wanlongmycin,the results turn out that Wanlongmycin could cause K⁺, Mg²⁺leakage, but the leakage of UV absorbing materials are not clear. That is to say, the primary effect of...