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首页> 美国卫生研究院文献>Journal of Bacteriology >H+/ATP stoichiometry of cowpea Rhizobium sp. strain 32H1 cells grown under nitrogen-fixing and nitrogen-nonfixing conditions.
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H+/ATP stoichiometry of cowpea Rhizobium sp. strain 32H1 cells grown under nitrogen-fixing and nitrogen-nonfixing conditions.

机译：cow豆根瘤菌的H + / ATP化学计量在固氮和非固氮条件下生长的32H1菌株。

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摘要

The obligate aerobe Cowpea Rhizobium sp. strain 32H1 in axenic culture is able to fix N2 when grown under 0.2% O2 but not when grown under 21% O2. It was, therefore, of interest to investigate ATP synthesis in these cells grown under the two conditions. When respiring in buffers having pHs ranging from 6 to 8.5, cells grown under either O2 tension maintained an intracellular pH more alkaline than the exterior. The transmembrane chemical gradient of H+ (delta pH) was essentially the same under both conditions of growth, decreasing from ca. 90 mV at medium pH 6 to ca. 30 mV at pH 8.5. However, the transmembrane electrical gradient (delta psi) was significantly higher in cells grown under 21% O2 (150 to 166 mV) than in cells grown under 0.2% O2, the latter being 16 mV at pH 6 and increasing to 88 mV at pH 8.5. Therefore, the proton motive force of 21% O2-grown cells ranged from 237 mV at external pH 6 to 185 mV at pH 8.5, compared with a proton motive force of 114 to 121 mV in the 0.2% O2-grown cells. The cells grown in 0.2% O2 had the same proton motive force whether tested at 21 or at 0.2% O2. The phosphorylation potential, calculated from the intracellular ATP, ADP, and Pi concentrations, was 424 mV in the 21% O2-grown cells and 436 mV in the 0.2% O2-grown cells. Thus, the 21% O2-grown cells translocated 1.8 to 2.3 H+/ATP synthesized by the H+-ATPase, whereas the H+/ATP ratio for 0.2% O2-grown cells was 3.7 to 3.8.
机译：专性好氧er豆Cow豆根瘤菌。当在0.2％的O2下生长时，无菌培养物中的32H1菌株能够固定N2，而在21％的O2下生长时不能固定N2。因此，研究在两种条件下生长的这些细胞中的ATP合成很有意义。当在pH值为6到8.5的缓冲液中呼吸时，在任一O2张力下生长的细胞都保持其细胞内pH值比外部碱度高。在两种生长条件下，H +的跨膜化学梯度（pH值δ）基本相同，从约3减小。 90 mV在中等pH值6至pH 8.5时为30 mV。但是，在21％O2（150至166 mV）下生长的细胞的跨膜电梯度（delta psi）明显高于在0.2％O2下生长的细胞，后者在pH 6时为16 mV，在pH 6时增加至88 mV。 8.5。因此，与0.2％O2生长的细胞中质子原动力为114到121 mV相比，21％O2生长的细胞的质子原动力为外部pH 6时的237 mV至pH 8.5时的185 mV。无论是在21％还是在0.2％O2下测试，在0.2％O2下生长的细胞具有相同的质子原动力。由细胞内ATP，ADP和Pi浓度计算得出的磷酸化电位在21％O2生长的细胞中为424 mV，在0.2％O2生长细胞中为436 mV。因此，21％的O2生长的细胞通过H + -ATPase合成的位置转移了1.8至2.3 H + / ATP，而0.2％的O2生长的细胞的H + / ATP比率为3.7至3.8。

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