| The strain of D5-2 was isolated and purified from Acacia confusa root nodule.Physiological and biochemical characteristics,inoculation in test tubes and potted seedlings,the analysis of 16S rDNA sequence,nifA gene,nifH gene,nodA gene and nodD gene were studied in this paper.The results showed that the strain can't use 3-ketolactose.In the experiments treated with hydrolysis of starch,liquefaction of gelatin and beef-protein,the strain shown negative response.The strain didn't return nitrate and utilized citrate,but generate acid in BTB tests.Two nitrogen sources and seven carbon sources could be utilized by D5-2.The strain could grow between 17?30?,and can stand the low temperature of 9?.It could grow on pH7.0-9.0,while couldn't grown on pH4.0-5.0.The experiment showed that the strain was tolerant to low concentrations of salt on medium containing 0.2%?1.0%.The result of Acacia confu.sa seeding inoculated with D5-2 in test tubes displayed that the strain was nodulated after 60 days.The root nodules were collected after cultured for 90 days.The average nodulation rate was 75.8%,nodulation amounts of single seeding was 2.76,nodule weight of single seeding was 8.0mg,nitrogenase activity was 19.86 nmol·g-1·min-1.The 16S rDNA sequence of D5-2 has 98%homology with 12 strains of Pseudomonas sp.According to the analysis of four genes,we found that the nifA gene has 72?78%similarity with Sinorhizobium,Bradyrhizobium sp.and Pseudomonas sp.,the nifH gene has 95?97%homology of these Rhizobium sp.and Bradyrhizobium.sp.,the strains from Bradyrhizobium sp.and Rhizobium sp.have 85-92%similarity with nodA gene,the nodD gene has 73%similarity of Azorhizobium caulinodans,and has 70%similarity of 4 Bradyrhizobium japonicum strains. |
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