Soybean plants host endosymbiotic dinitrogen (N2)-fixing bacteria from the genus Bradyrhizobium. Under oxygen-limiting conditions, Bradyrhizobium diazoefficiens and Bradyrhizobium japonicum perform denitrification by sequentially reducing nitrate (NO3–) to nitrous oxide (N2O) or N2. The anaerobic reduction of NO3– to N2O was previously shown to be lower in B. japonicum than in B. diazoefficiens due to impaired periplasmic nitrate reductase (Nap) activity in B. japonicum. We herein demonstrated that impaired Nap activity in B. japonicum was due to low Nap protein levels, which may be related to a decline in the production of FixP and FixO proteins by the cbb3-type oxidase.

中文翻译：

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日本慢生根瘤菌反硝化过程中周质硝酸还原酶水平低于重氮慢生根瘤菌

大豆植物宿主来自慢生根瘤菌属的内共生二氮 (N2) 固定细菌。在限氧条件下，慢生根瘤菌和慢生根瘤菌通过将硝酸盐 (NO3–) 依次还原为氧化亚氮 (N2O) 或 N2 来进行反硝化作用。由于 B. japonicum 中的周质硝酸还原酶 (Nap) 活性受损，先前表明在 B. japonicum 中 NO3- 到 N2O 的厌氧还原比在 B. diazoefficiens 中要低。我们在此证明了 B. japonicum 中 Nap 活性受损是由于低 Nap 蛋白水平，这可能与 cbb3 型氧化酶产生的 FixP 和 FixO 蛋白的减少有关。