| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1986: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
The atomospheric nitrogen is fixed and utilized symbiotically by Rhizobium nodulated leguminous plant or non-symbiotically by free-living N_2-fixing bacteria(for example;Azotobacter,Klebsiella etc.) in rhizosphere. The utilization effeciency of fixed nitrogen in symbiotic system as Rhizobium-leguminous plant is higher than in non-symbiotic system as N_2-fixing bacteria.
Nitrogen fixation in non-symbiotic bacterial cells is stable under oxigen containing atomosphere, though Rhizobium cannot fix nitrogen under free-living state and in air. The establishment of symbiotic system with the cells, undisturbed N_2-fixation in air, and plants may have many benefical merits. Then, the analysis of nodulation mechanism of Rhizobium was performed in the first step.
Rhizobium trifolii Qnl(Nod^+,Fix^-), a mutant derived from R. trifolii 4S(Nod^+,Fix^+,wild type), formed pseudonodules on Trifolium repens, however the one formed normal nodules on Phaseolus vulgaris except lacking of nitrogen fixing ability. It was supposed that strain Qn1 confused host specificity-gene(hsn) from the region of nod-gene. Gene library of total DNA from R. trifolii 4S was prepared for obtaining normal nodulation gene as probe. Nod-gene has been screening out from the gene library by triparental-mating technique using a mutant, R. trifolii H1(sym-plasmid cured), as a recipient. Nod region from strain Qn1 will be able to determine by hybridization with the nod-gene probe and also analyse the hsn region including in nod-gene.
We obtained prospects of success that the confused host specific nodulation gene containing in strain Qn1 transfers to non-symbiotic N_2-fixing bacteria in this study.
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