根瘤菌铁转运代谢及其调控机制研究进展

Advances in Mechanisms and Regulation of Iron Uptake and Metabolism in Rhizobia

根瘤菌是一类可以与豆科植物高效共生固氮的兼性共生细菌,在全球氮循环及绿色可持续农业中发挥重要作用。为了适应土壤、根圈和宿主体内等多变的生活环境,根瘤菌对营养物质的感知和获取能力至关重要。铁不仅是根瘤菌在土壤中生长繁殖的限制性营养元素,更直接参与固氮酶、豆血红蛋白、电子呼吸链等与共生固氮密切相关功能蛋白的合成。因此,根瘤菌在自生和共生阶段如何获取自身所需的铁是生物固氮领域所特别关注的重要研究内容。综述了近年来有关根瘤菌中Fe^2+、Fe^3+-铁载体复合物、血红素吸收途径以及RirA/Irr等参与铁稳态调控方面的研究进展并进行归纳分析,以期为后续的研究工作提供借鉴。

Rhizobia are a collection of facultative symbiotic bacteria that possess the ability to establish symbiotic associations with legume hosts and carry out nitrogen fixation.Hence,they play important roles in the global nitrogen cycle and green sustainable agriculture.In order to adapt to the changing living environment such as soil,rhizosphere and infected host cells,it is vital for rhizobia to develop powerful strategies to sense and acquire nutrients.Iron is not only a limiting nutrient element for rhizobial growth and reproduction in the soil,but also directly involved in the synthesis of functional proteins closely related to symbiotic nitrogen fixation,such as nitrogenase,leghemoglobin and electronic respiratory chain components.Therefore,how rhizobia obtain iron under free-living and symbiotic conditions is highly concerned by scientists in the field of biological nitrogen fixation.Here we review recent researches on the uptake pathways of iron in different types such as Fe^2+,Fe^3+-siderophore complex,and heme and summarize regulation mechanisms of iron homeostasis mediated by RirA,Irr and other regulators in rhizobia,aiming to provide reference and insight for subsequent intensive researches.