单细胞稳定同位素标记技术在固氮微生物中的应用研究

Application of single-cell stable isotope probing approach to investigate N2-fixing microorganisms

生物固氮是指固氮微生物将大气中氮气还原为生物可利用氨的过程,是环境中新氮的主要来源,调控初级生产力并影响氮储库的收支平衡。由于环境中大部分固氮微生物不可纯培养,不依赖培养且具有高空间分辨率水平的单细胞技术,成为研究固氮微生物的有力手段。15N2稳定同位素标记技术,以微生物对15N的同化量或速率为依据,是表征微生物固氮活性的最直接手段。本文对15N2稳定同位素标记结合两种单细胞技术,即纳米二次离子质谱(NanoSIMS)和单细胞拉曼光谱,用于固氮微生物研究的最新进展进行了综述,内容包括揭示环境中高活性固氮微生物、空间分布、与其他生物的共生关系、细胞生理状态等,并进一步对近期发展的基于单细胞拉曼光谱的固氮微生物研究进行了展望。

Biological nitrogen fixation,a process through which nitrogen-fixing microorganisms reduce atmospheric nitrogen to bioavailable ammonia,is the main source of“new”nitrogen in the environment,regulates primary productivity and thus affects the balance of nitrogen storage.Because most of nitrogen-fixing microorganisms in the environments are yet uncultured,culture-independent single-cell techniques with a high-level spatial resolution have become a powerful tool for studying nitrogen-fixing microorganisms.In addition,15N2-stable isotope probing(SIP)provides a very direct means to characterize nitrogen fixation activity based on the amount or rate of 15N assimilated by microorganisms.This article reviews the latest progresses in applying two single-cell techniques of nanosecondary ion mass spectroscopy(NanoSIMS)and Raman spectroscopy integrated with 15N2-SIP for studies of nitrogen-fixing microorganisms,including the discovery of novel active nitrogen-fixing species and their spatial distribution in the environment,symbiotic relationship with other organisms,cellular physiological states,etc.Perspective on future study of nitrogen-fixing microorganisms by single-cell Raman spectroscopy is provided.