紫云英根瘤菌109菌株吸氢特性及碳底物的调节

Characteristics of H_(2)-Uptake System of Rhizobium astragalus 109

紫云英根瘤菌109菌株完整细胞的吸氧活性,在空气气相中衰减快,加氢或降低温度,衰减延缓。完整细胞的吸氢反应受体,包括甲基蓝、氧、铁氰化钾、TTC、甲基紫精、Cyt C_3、硝酸钾、DCPIP和反丁烯二酸盐的表现不相同。当氧为受体时,气相氧浓度为5％,吸氢值最大,甲基蓝为受体时,吸氢活性高。另外,氧为受体的吸氢受到碳水化合物抑制,并与基础吸氧速率相关。紫云英根瘤菌的氢氧化与碳水化合物氧化竞争电子传递途径。

The H_2-uptake activity in suspension ofRhizobium astragalus strain 109 was sensitive toatmosphere phase at room temperature. Butadding H_2 or keeping the suspension at 4℃could decrease the decline rate (Fig. 1,2). Intact cells of R. astragalus took up H_2using O_2 as phyiological acceptor and ap-peared to be similar to Bradyrhizobium japoni-cum strain. The optimum concentration ofgas-phase O_2 in reaction was about 5% (v/v)(Fig. 3). Neither C_2H_2 nor CO_2 affected theO_2-dependent H_2-uptake activity (Fig. 5). Many non-physiological electron acceptorswith positive redox potential such as methyleneblue (MB), ferricyanide, triphenyltetrazolium,nitrate, dichlorophenolindophenol and furma-tate also supported H_2-uptake by the intactcells. UsIng MB as acceptor, the rate ofH_2-uptake was greater than that using O_2,and the apparent K_m value for MB was 0. 167mmol/L. But using other acceptors the ratesof H_2-uptake were lower than that using O_2(Table 1). No H_2 evolution was observedfrom the reaction mixture containing intactcell suspension, and methyl or benzyl violo-gens were reduced. However the H_2-uptakewas observed from the mixture containingmethyl viologen. GJuconate and succinate inhibited H_2-uptake. But the inhibition depended on eitherthe incubation time of cells with the carboncompounds or the background rates of O_2-uptake by cell suspension (Fig.7--9). Therelationship between the H_2 oxidation andrespiration was discussed.