ABSTRACT
Twenty-eight moderately halophilic bacteria isolated from salt lakes in Xinjiang Regions were analyzed by 16S rDNA PCR-RFLP in comparison with nine reference strains of related species. The 16S rRNA PCR products of the tested stains were digested by four restriction enzymes (AluI, HinfI, RsaI and HaeⅢ). The results showed that all tested strains were clustered into three groups at 74% similarity level. Group I included 2 reference strains Chromohalobacter marismortui, Nesterenkonia halobia and new isolate CI. Group Ⅱ included seven type strains belonging to Halomonas and eight new isolates. Group Ⅲ included ninteen new isolates.
ABSTRACT
The direct ELISA was used to detect cells from pure cultures and nodules of Bradyrhizobium japonicum USDA110 and Rhizobium fredii RTt50. The optimum dilution of enzyme-linked conjugates, HRP-Ab110 and HRP-Ab50, was 1:3200 and 1:800 respectively. The optimum dilution of antibodies, Ab110 and Ab50, was 1:3200 and 1:800 separately. The optimum concentrations of antigens, USDA110 and RTt50, were both 6?10~7 cells/ml. Slow and fast-growing soybean rhizobiz can be detected and differentiated specifically by direct ELISA. Among a few strains of these two groups of soybean rhizobia, cross-reaction occurred. This was eliminated by absorption, so that specific strain could be identified by ELISA. The minimal concentration of antigen for detected was 2?10~5 cells/ml. It was found that nodules preserved by drying over silica gel or freezing were equally good, without loss in sensitivity of ELISA. ELISA was used to study the competition of USDA110 and RTt50 with indigenous rhizobia in soil pot experiment. Nodule occupacy of USDA110 ranged from 75-87.5% in different growing season of soybean and RTt50 ranged from 25-45%. The result showed that ELISA was more sensitive than agglutination.