Metabolism of Escherichia coli is interfered by Bacillus subtilis glnA gene / 生物工程学报

A recombinant strain Escherichia coli DH5alpha(pMD19-glnA) including Bacillus subtilis glnA gene was constructed. Capillary electrophoresis and nuclear magnetic resonance were used to determine qualitatively the product of transformation by recombinant strain, and the relative level of mRNA expression of glnA was also determined by fluorescence quantitative RT-PCR. Subsequently, SDS-PAGE (polyacrylamide gel electrophoresis) was used to analysis the relative level of protein. Surprisingly, there was no increase of glutamine production in this recombinant strain, but an obvious increase in the GABA (gamma-aminobutyric acid ) production. It was showed in the experiment that protein expression of the glutamine synthetase did not increase, although glnA gene can be transcribed normally in this recombined strain. The phenomenon of exogenous glnA gene interfering metabolism of Escherichia coli was worthy of further study.

ENZYME-LINKED LMMUNOSORBENT ASSAY (ELISA) FOR SOYBEAN RHIZOBIA STRAIN IDENTIFICATION / 微生物学通报

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.