Studies On The Metabolite And Antifungal Activity Of Xenorhabdus Nematophilus YL001 From Entomopathogenic Nematodes

The symbiotic bacterium associated with entomopathogenic nematode is a Gram-negative symbiotic bacterium. Xenorhabdus and Photorhabdus are two kinds of bacterial genera mutually associated with infective juveniles of entomopathogenic nematodes from the genera Steinernema and Heterorhabditis, respectively. Manifold bioactive secondary metabolites produced by Xenorhabdus and Photorhabdus have been reported . These metabolites have diverse chemical structures, furthermore a wide range of bioactivities of medicinal and agricultural significance, such as antibiotic, antimycotic, insecticidal, nematicidal, ant ulcer, antineoplastic and antiviral. The symbionts have become an important new type biologic resource with the potential of exploitation and the prospect of application. In this paper, the symbiotic bacteria , Xenorhabdus nematophila,coded YL001 and associated with Steinernema sp YL001 which are separated from Shaanxi province are studied in some extent, and the content includes metabolites bioactivities, separation and identification of bioactive component, antifungal acting manner and acting mechanism , and fungicidal preparation of the symbiotic bacteria. The primary result and conclusion are as follows:1. The antifungal activities of extracellular metabolic products from Xenorhabdus nematophila code YL001, are tested in vitro and in vivo.The bioassay results indicates that the supernatant fermentation inhibit mycelia growth of 15 species investigated plant-pathogenic fungal in vitro. It especially could markedly inhibit the mycelia growth to Botrytis cinerea and Phytophthora capsici. Their EC₅₀ value against Botrytis cinerea and Phytophthora capsici are 53.54 mg·L^-1 and 90.39 mg·L^-1, respectively. The spore germination of 6 species investigated plant-pathogenic fungal are inhibited. The spore germination EC₅₀ value against Botrytis cinerea and Alternaria alternata are 16.97 mg·L^-1 and 21.87 mg·L^-1, respectively. In addition, the protective effect and therapeutic effect of the fermentation products at 0.389g·L^-1 against the Botrytis cinerea are 74.98% and 63.50% on tomato, respectively. Finally, the protective effect and therapeutic effect of the fermentation products against the Botrytis cinerea are 65.11% and 54.64% on cucumber in glasshouse pot...