Estimation of gus marked bradyrhizobial number by phenol extraction of GUS metabolite
1997
Minagawa, R. (Niigata Univ. (Japan). Faculty of Agriculture) | Isoda, K. | Ohtake, N. | Yamada, S. | Ikarashi, T. | Minamisawa, K. | Ohyama, T.
Bradyrhizobium japonicum strain 61 A 124 a, in which Escherichia coli gus A gene was introduced to Bradyrhizobium japonicum, absorbs and hydrolyzes GUS-substrate (X-Gluc), and precipitates an indigo pigment. We attempted to use the absorbance of the accumulated GUS-metabolite as an indicator of the rhizobial number in soil. The accumulated indigo blue metabolite in rhizobia were extracted by phenol-water after they are incubated with X-Gluc for 4 d. The absorbance of the extracted blue pigment in the phenol layer was measured at 645 nm. The initial number of rhizobia and the absorbance of the GUS-metabolite was positively correlated either in cultured 61 A 124 a or in the various types of soil inoculated with 61 A 124 a strain. IN the presence of soil, the absorbance per rhizobial number was low compared with the pure culture. Therefore, a standard curve between rhizobial number of 61 A 124 a and the absorbance should be made fro every soil sample. During incubation with X-Gluc, rhizobia did not proliferate because of the depression effect on cell growth of N,N-dimethylformamide and the accumulation of indigo pigment
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