The Research Of An Endophytic Bacterial Strain With Antifungal Activity From The Vaccinium Uliginosum

The research is mainly in the area of the isolation and identification of endophytic bacteria from Vaccinium spp..There are several factors influencing the isolation result, such as different Vaccinium spp., different parts of Vaccinium spp.,the surface sterilization,and the separation methods. A strain of endophytic bacteria with a good anti-fungal ability is isolated from Vaccinium uliginosum. The strain is effective to inhibit the growth of all the twelve pathogens. The inhibition rate, among the 12 fungal pathogens, ranges from 22.7-70.5%, especially the inhibition percentage to Uromyces appendiculatu is 70.5%.The pathogen of the leafspot Cylindrocladium colhounii and Pestalotiopsis sp. are also inhibited by this strain, of which the inbition percentage is 68.6 % and 57.7%.It is identified as Serratia marcescens using the 16s rDNA sequence homology and through its physiological and biochemical characteristics. The strain is named with S. marcescens. DUT. Through the alignment and cladistic analysis of homologous nucleotide sequences of known Serratia marcescens, it is possibly to be a novel subspecies of S. marcescens. To our knowledge,this is the first time that an endophytic S. marcescens was isolated from a wild blueberry in China, and may also represent a novel introduction to the world.The best growing condition of strain DUT is: grow for 8-24 hours under pH 7 and 28℃.The best composition of carbon ,nitrogen and other ingredients are glucose 10 g/L, ammonium sulfate 10 g/L, citrate sodium 1g/L, disodic phosphate 0.3 g/L, magnesium sulfate 0.25 g/L.Marking the strain DUT with Rifampicin to determine its colonization in Vaccinium spp. ,the result indicts that the strain DUT could colonize in Vaccinium spp..The experiment result confirms that the strain DUT produces chitinase and the enzyme activity is 20.11 U/mL after 3 day fermentation,adopting DNS method. By pcr method, the chiA and chiB genes are obtained. After the bioinformatic anlysis, the data certificate that they both own the CDD of Glycohydrolase.