Abstract
Rhizobium meliloti 102 F 51, the symbiotic partner of alfalfa, was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and UV-irradiation. Three group of mutants which form white, white-pink and red nodules were selected. The adetylene reduction activity, nodulation activity, amount of heme synthesis during the nodulation, and ${\delta}-aminolevulinic$ acid synthetase (ALAS) and ${\delta}-aminolevulinic$ acid dehydratase (ALAD) activities in free living rhizobia and bacteroid states of the each group of mutants were compared. The mutants forming white nodules showed lower acetylene reduction activity compared to those of red nodule forming mutants. The two key enzymes for the heme synthetic pathway, ALAS and ALAD activities of the mutants forming red nodules was much higher than those of the mutants forming white nodules in bacteroid state, however no significant difference was observed in free living state. In the nodules the ALAS was detected only in bacteroid fraction, while ALAD was detected both in bacteroid and plant fraction. ALAS was dramatically increased with the heme synthesis during the nodulation, while ALAD was decreased in plant fraction but slight increase was observed in bacteroid fraction.
Rhizobium melitoli 102F51에 N-methyl-N'-nitro-N-nitrosoguanidine 및 UV를 처리하여 heme 합성 특성이 다른 세 그룹의 mutant 즉 백색, 적백색 및 적색근류형성 mutant를 선별하여 이들 중 mutant들의 acetylene 환원력, 및 ${\delta}-aminolevulinic$ acid dehydratase (ALAD)를 free living 및 bacteriod 상태하에서 서로 비교하였다. 백색 근류를 형성하는 mutant는 적색 근류형성 mutant에 비하여 acetylene 환원력이 훨씬 낮았으며 ALAS 및 ALAD 활성은 free-living 상태에서는 각 mutant group 사이에서 큰 차이를 보이지 않았으나 bacteriod 상태에서는 백색근류생성 mutant에서 적색 근류형성 mutant group에 비하여 ALAS 및 ALAD 공히 현저히 낮았다. 근류에서 ALAS 활성은 heme 합성양에 비례하여 급진적으로 증가하였으나 ALAD 활성은 plant fraction에서는 감소하는 반면 bacteroid fraction에서는 완만하게 증가하였다.
