海洋微生物铁载体的研究进展

The Research Advance of Siderophores in Marine Microbes

铁是影响初级生产力的主要限制性因子之一,其在海洋环境中的分布具有空间异质性。由于铁在海洋中主要以溶解度较低、易沉降的三价态(Fe)形式存在,因此溶解铁对海洋生物而言是一种稀缺资源。为了获得生命代谢所需的铁,微生物进化出多种铁摄取的策略来满足需求,其中铁载体(siderophores)是最典型的代表。铁载体作为重要的代谢辅因子,除了铁循环以外,也强烈影响着其他元素的循环。基于铁载体的重要性,深入理解它的合成、转运和调控机制是系统认识海洋铁循环和生命过程的重要环节之一。本文以近20年的研究为重点,总结了铁载体的最新进展,包括其类型、合成/运输系统、获取途径、调控机制以及铁载体的功能与应用,旨在更好地认识铁载体在海洋微生物生态学过程中的作用,加深对海洋铁循环动力学机制的理解。

The vast majority of bacteria require iron for growth.Iron is an essential element required for key biological processes including amino acid synthesis,oxygen transport,respiration,nitrogen fixation,methanogenesis,the citric acid cycle,photosynthesis,and DNA biosynthesis.However,obtaining iron presents challenges for the majority of microorganisms.In the ocean,the distribution of iron in the marine environment is spatially heterogeneous,which is one of the main limiting factors affecting marine primary productivity.Dissolved iron is a scarce resource for marine creatures because it is mainly present as a less soluble trivalent state(Fe),which makes it prone to settling and being“removed”.Marine microorganisms are presented with unique challenges to obtain essential iron ions required to survive and thrive in the ocean.To obtain enough iron source for life metabolism,microorganisms have evolved many ways to meet the demand for iron intake,among which siderophores is the most representative one.Siderophores are low molecular mass iron-binding ligands produced by marine bacteria.Microbial siderophores are multidentate Fechelators used by microbes during siderophoremediated assimilation.They possess high affinity and selectivity for Fe.Among them,marine siderophoremediated microbial iron uptake allows marine microbes to proliferate and survive in the iron-deficient marine environments.Being an important metabolic cofactor,siderophores also strongly influences the circulation of other elements.In order to better understand the role of siderophores in marine microbial ecology and deepen our understanding of marine iron cycle dynamics,this paper summarizes the types of siderophores such as hydroxamates,catecholates and carboxylates,two main siderophores synthesis pathways of microorganism and the mechanism of regulating siderophores synthesis,describes the transmembrane transport process of siderophores and several functional protein elements,the functions of siderophores such as anti-oxidative stress,regulation of pathogen virulence,formation of multifunctional iron and sulfur polymers,and anti-pathogens and so on.Although siderophores have been studied and discussed,further research can be carried out in the following aspects,such as the interaction mechanism between siderophores and marine microorganisms,the application of synthetic biology,and the coupling ability of siderophores behavior with other elements.