Iron Uptake and Metabolism in the Bradyrhizobium/Soybean Symbiosis

含铁蛋白质在氮中占据重要地位- 固定细菌和它们各自的植物之间的共生关系 hosts. 虽然土壤中含有丰富的铁， 由于铁在生物pH下溶解度低， 在有氧条件下。 铁的获得研究， 关于经济上重要的共生体是针对 回答三个问题：1）根瘤菌细胞如何获得铁 作为自由生活的微生物，它们必须竞争 与其他土壤居民的营养2）根瘤菌如何获得 铁作为共生体和3）铁调节基因表达？ 关于铁载体利用的研究仍在继续 B分别以柠檬酸、铁铬和玫瑰藻酸为铁源。 以及铁调控基因参与 铁吸收 本研究：1）进一步表征 从生物化学上讲，铁的获得是通过自由生活和 B的共生细胞2）鉴定和表征 与铁获得有关的基因，包括那些编码 铁诱导的外膜蛋白，和3）研究 铁对基因表达的调控 世界对蛋白质的需求不断增加， 生产氮肥的费用导致了 生物固氮的广泛兴趣。 虽然 固氮慢生根瘤菌/豆科植物共生体 在温带地区， 世界上，共生的许多方面仍然很差， 明白 铁在动物/病原体中的重要性 相互作用现在已经很好地建立起来;这种金属在 固氮根瘤菌和豆科植物的共生关系才刚刚开始 有待探索 这里提出的研究提供了一个更好的 了解铁在调节共生过程中的作用 互动 这样的理解阐明了根瘤菌如何 以及它们如何与植物相互作用 宿主建立有效的共生关系。 这对于以下方面至关重要： 任何努力，以工程师一个更好的共生，并为最终 将共生关系扩展到其他植物宿主。

Iron-containing proteins figure prominently in the nitrogen- fixing symbioses between bacteria and their respective plant hosts. Although iron is abundant in the soil, the acquisition of iron is problematic due to its low solubility at biological pH under aerobic conditions. The study of iron acquisition as it pertains to economically important symbioses is directed at answering three questions: 1) how do rhizobial cells acquire iron as free-living microorganisms where they must compete for this nutrient with other soil inhabitants 2) how do rhizobia acquire iron as symbionts and 3) does iron regulate gene expression? Studies are continuing on the utilization of the siderophores citrate, ferrichrome and rhodoturulate as iron sources by B. japonicum as well as on the iron regulation of genes involved in iron uptake. This research: 1) further characterizes biochemically the acquisition of iron by both free-living and symbiotic cells of B. japonicum, 2) identifies and characterizes genes involved in iron acquisition, including those which encode iron-inducible outer membrane proteins, and 3) investigates the control of gene expression by iron. The increasing world demand for protein and the increasing expense of producing nitrogen fertilizer has resulted in a widespread interest in biological nitrogen fixation. Although the nitrogen-fixing Bradyrhizobium/legume symbioses supply much of the fixed nitrogen for agriculture in the temperate regions of the world, many aspects of the symbioses are still poorly understood. The importance of iron in animal/pathogen interactions is now well established; the role of this metal in the nitrogen-fixing rhizobial/legume symbioses is just beginning to be explored. The research proposed here provides for a better understanding of the role of iron in regulating the symbiotic interaction. Such an understanding elucidates how rhizobia survive in the soil as well as how they interact with their plant host to establish an effective symbiosis. This is essential to any efforts to engineer a better symbiosis and for the ultimate extension of the symbiosis to other plant hosts.