| As a big group of microbe inhabiting in the living tissues of plants, endophytes have no negative effects on the host plants during their whole life history or some phases. Because of their particularity of living environment, endophytes are different from the environal microorganisms on biological function and physiology. During the long run road of the evolution, a symbiosis system has formed between endophyte and host, the change of environment conditions and host metabolisms affect the change of genus and metabolism in endophytes correspondingly. It is a consent that endophytes are a special microbe resource . Endophytes are a potential source of novel anti-microbe chemistry and biology to assist in helping solve not only human health, but plant and animal health problems also. Now we are just at the beginning of the researching on endophytes, we can not take full advantages of endophytes because many of their characters have not been understood, so research on the anti-microbe endophytes not only brings vast social profits but also has realistic theoretic significance.In this scientific dissertation, medicinal plant Dendrobium tissues were chosen as the materials for separation of antifungal endophytes.All, four of produced wide-spectrum antifungal endophytes isolated from Dendrobium..They are DEB-1,DEB-2,DEB-3,DEB-4, and are indentified by physiological, biochemical and molecular biology techniques. The antifungal function of the strain DEB-2 is tentative studied. The results were as follows.1. By tissue surface-sterilized, about 46 strains endophytes isolated from the stem tissues of Dendrobium nobile Lindle and Dendrobium fimbriatum Hook. Of these 46 isolates, there were 5 endophytic bacteria and 41 endophytic fungi. Amongst 5 isolates endophytic bacteria we have screened 4 endophytes which have antifungal activities they were DEB-1,DEB-2,DEB-3,DEB-4.2. Identified by physiological and biochemical techniques, the strains DEB-1,DEB-2,DEB-3, DEB-4 all have the following results: thalli shape of the strains were bacilliform, bacterial spore were bulged at center or near the port of thalli, gram staining, mobility, catalase, amylase and V P assays were positive, utilized glucose, mannite and xylose for growth and produced acid , nitrous acid deoxidized assays were positive, oxygen was a critical growth factor, thalli shape didn't changed on different culture medium, 30-35℃ was the optimal growth temperature range.16S-23S rDNA of the strains DEB-1,DEB-2, DEB-3,DEB-4 were sequenced. Sequence length was about 240bp, they all were 96-99% homology to the Bacillus polyfermenticus and 96%-98% homology to other Bacillu sp. in GenBank nucleotide sequences databases. These ITS sequences were employed for the studies of the strains gene genealogy.The gene tree was phylogenetically generated from ITS data.3. The antifungal agent produced by strain DEB-2 were wide-spectrum antibacterials.They were strong effects against some phytopathogen , such as Botrytis cinerea Pers.,Botrytis cinerea Pers, F.graminearum, Rhizoctonia cerealis Vander Ho even, Alternaria, F.lycoersici, and demic pathogenic fungi Candidaalbicans, and also against the mildew Aspergillus niger which cause foodstuff decayed. At the same time they showed good effects of antifungal against several endophytic fungi.4. The strain DEB-2 always have the function of antifungal after undergo 23 transfer of culture. The effect of antifungal is stabile. It caused the inhabited morphological abnormalities of characteristic bulges, thickening, collapse or swelling and stimulation of branching on the hypha... |
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