Symbiotic nitrogen fixation by rhizobia in legume root nodules injects approximately 40 million tonnes of nitrogen into agricultural systems each year. In exchange for reduced nitrogen from the bacteria, the plant provides rhizobia with reduced carbon and all the essential nutrients required for bacterial metabolism. Symbiotic nitrogen fixation requires exquisite integration of plant and bacterial metabolism. Central to this integration are transporters of both the plant and the rhizobia, which transfer elements and compounds across various plant membranes and the two bacterial membranes. Here we review current knowledge of legume and rhizobial transport and metabolism as they relate to symbiotic nitrogen fixation. Although all legume-rhizobia symbioses have many metabolic features in common, there are also interesting differences between them, which show that evolution has solved metabolic problems in different ways to achieve effective symbiosis in different systems.

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豆科植物-根瘤菌共生体的运输和代谢

豆科植物根瘤中的根瘤菌共生固氮每年向农业系统注入约 4000 万吨氮。作为细菌减少氮的交换，植物为根瘤菌提供减少的碳和细菌代谢所需的所有必需营养素。共生固氮需要植物和细菌代谢的完美结合。这种整合的核心是植物和根瘤菌的转运蛋白，它们将元素和化合物转移到各种植物膜和两个细菌膜上。在这里，我们回顾了与共生固氮有关的豆科植物和根瘤菌运输和代谢的当前知识。尽管所有豆科植物-根瘤菌共生体都有许多共同的代谢特征，但它们之间也存在有趣的差异，