Isolation and Preliminary Identification of Endophytic Bacteria in the Root Nodule of Paulownia

【Objective】In order to explore the symbiotic nitrogen fixation system of non-leguminous plants Paulownia and microorganism, a preliminary study was carried out on isolated culture conditions and the phylogenetic position of endophyic bacteria in Paulowia root nodules.【Method】The endophytic bacteria isolated and purified from the root nodules of Paulownia collected from Qinzhou of Guangxi Province were subjected to traditional physiological and biochemical studies and 16S rDNA phylogenetic analysis.【Result】In the nine strains of endophytic bacteria isolated and purified, most of the bacterial strains could make good use of 8 carbon sources; 78% of the bacterial strains could use ammonium salt, and 89% of the bacterial strains could use nitrate. All tested bacterial strains were negative in the 3-ketolactose and starch hydrolysis test; 89% of the strains could use citrate. Except that the bacterial strains PG-7 produced alkali, the rest of bacterial strains produced acid in the B.T.B reaction; 33% of the strains could reduce nitrate; 56% of the strains grew well on beef extract peptone medium, and most strains have the general physiological and biochemical characteristics of leguminous rhizobium after identification. According to 16S rDNA complete sequence analysis, nine bacterial strains can be divided into four bacteria genera, among which the bacterial stains PG-1 and PG-2 belong to Agrobacterium, PG-3, PG-5, PG-6, PG-8 and PG-9 belong to Rhizobium, PG-4 belongs to Herbaspirillum and PG-7 belongs to Burkholderia.【Conclusion】The endophytic bacteria isolated from the same root nodule have great differences in their physiological and biochemical characteristics of endogenous bacteria , and showed genetic diversity.