| Yang mei shuang disease is very commom on Tremella fuciformis artificial bed-log in Gutian, Fujian Province. This disease could reduce tremella fuciformis production. But we knew very little about this disease at present, which brought great difficulty to the prevention and control of it. For the disease, this dissertation focused particularly on studies on the pathogen separation, the causes of the disease, strain identification, antibacterial activity, optimization of fermentation condition and the stability of fermentation products, the main results are as follows:1. Three actinomycetes strains Js-1T, Js-2 and Js-3 were isolated from the Tremella fuciformis artificial bed-log which was infected with the disease by dilution method. The colonies characteristics and cultural characteristics of these strains were the same. The 16S rDNA of three strains were digested same by PST I and ECORV, so these strains were repeated strains. Strain Js-1T was confirmed to be the pathogen of this disease through Koch’s rules. Strain Js-1Thad strong inhibition on xianghui and tremella gemma, which could be the cause of the disease.2. Strain Js-1Twas identified by polyphasic taxonomy technology(1) BLAST online showed that strain Js-1T has high similarity values with corresponding Streptomyces species. And the isolate was closest to the type strains Streptomyces hebeiensis strain YIM001T, Streptomyces hebeiensis strain NBRC101006T and Streptomyces albus subsp.pathocidicus strain NBRC13812T. However, the similarity between strain Js-1T and other type strains was all below 97%. What’s more, strain Js-1T falled into one distinct subclade with these three and other related type strains of the genus Streptomyces in the phylogenetic tree. All of these suggested that strain Js-1T might be a novel species.(2) Strain Js-1T develops concentric colonies, white aerial mycelium and extensively branched substrate mycelium and on PDA agar. Long, straight to rectiflexibiles spore chains differentiate from aerial mycelium, and each spore chain contained more than 10 spores. The cylindric shaped spores with dimensions of 0.5-0.8μm, smooth surface and were non-motile. Colonies develop well on potato agar, yeast-malt extract agar, oatmeal agar, glucose asparagine, GYES and glycerol-asparagine agar except for inorganic salts-starch agar and gauze’s no.1 agar. Strain Js-1T producted diffusible pigments on potato agar, yeast-malt extract agar and glycerol-asparagine agar.(3) It can grow at 15-40℃ but can not grow at 10℃ or 45℃. Growth occurs in the pH rage 5-10 and below the presence of 7% NaCl. D-Glucose, D-Fructose, D-Mannose, Maltose and Arabinose can be used as sole carbon sources for growth, but D-Sorbitol, L-Inositol, Sucrose, Raffinose can not be used as carbon sources. Starch can not be metabolized. Coagulation and peptonization of milk, liquefaction of gelation and catalase are positive. Melanin pigments were not produced on tyrosine agar plates. These morphological characteristics indicated that strain Js-1T was different from the other species of Streptomyces genus.(4) The main cellular fatty acids of strain Js-1T are (18:1 w6c|18:1 w7c) (80.60%),16:0 (7.02%),16:0 iso (2.63%),15:0 iso (2.34%),15:0 anteiso (1.37%).(5) The G+C content of the DNA is 70.1 mol%. The DNA-DNA relatedness between strain Js-1T and Streptomyces hebeiensis strain YIM001T was only 47.2%, between strain Js-1T and Streptomyces albus subsp.pathocidicus strain CGMCC4.1633 was only 35.4%.The results of polyphasic taxonomy showed that strain Js-1T was a novel species of genus Streptomyces, for the name Streptomyces fujianensis sp.nov. And strain Js-1 was deposited in the Collection Center of Typical Cultures, China (CCTCC) as strain CCTCC M 2011365T.3. The antibacterial activity of strain Js-1T was determined. The result showed that strain Js-1T had strong inhibition against these tested strains. The diameter of Escherichia coli and Bacillus subtilis was respectively 2.76cm and 1.26cm. The diameter of Sclerotinia sclerotiorum, Mycogone perniciosa, Pyricularia grisea, Trichoderma viride, Rhizopus stolonir was respectively 4.29cm,4.07cm,3.85cm, 3.37cm and 2.90cm. In addition, strain Js-1T had antibacterial activity to Yeast, Fusarium spp and Banana vasicular wilt. The fermentation products of strain Js-1T had high inhibition to Pleurotus eryngii, Volvariella volvacea, Flammulina velutipes, Lentinual edodes and Agaricus bisporus.4. The fermentation conditions of strain Js-1T were studied. The single factor experiment indicated that the optimal carbon source was 25.0g/L maltose and the optimal nitrogen source was 2.0g/L KNO3. The optimal fermenting conditions were temperature 28℃, pH 7, and 100ml liquid medium in 250ml flake.5. The fermentation product of strain Js-1T was stable to heat, and the antibacterial activity had only reduced 11% after heated for 20min at 121℃. But the product was not stable to acid or alkaline-base environment. |
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