Epsilon-Fe2O3 is a novel intermediate for magnetite biosynthesis in magnetotactic bacteria

Tong Wen,Wei Jiang,Junquan Liu,Yunpeng Zhang,Yuanyuan Geng,Jilun Li,Ying Li,Abdul Basit,Jiesheng Tian,Jing Ju

doi:10.1186/s40824-019-0162-1

Abstract

BackgroundNatural biological magnetite nanoparticles are widely distributed from microorganisms to humans. It is found to be very important in organisms, especially in navigation. Moreover, purified magnetite nanoparticles also have potential applications in bioengineering and biomedicine. Magnetotactic bacteria (MTB) is considered one of the most abundant species around the world which can form intracellular membrane enveloped magnetic nanoparticles, referred to as magnetosomes. To our knowledge, the biomineralization of magnetosome in MTB involves a serious of genes located on a large unstable genomic region named magnetosome island, which specially exists in MTB. The magnetite core of magnetosome formed via a Fe (III) ion intermediates, for instance, α-Fe2O3 and ferrihydrite. Though the biosynthesis of magnetosome represents a general biomineralization mechanism of biogenic magnetite, knowledge of magnetosome biosynthesis and biomineralization remains very limited.MethodCells used in this study were cultured in a 7.5-L bioreactor, samples for intermediate capture were taken each certain time interval after the generation of magnetosome biosynthesis condition. High-resolution transmission electron microscopy were used to analyze the detailed structure of magnetosomes. The parameters of the crystal structures were obtained by Fast Fourier Transform analyses.ResultsIn this study, we identified a novel intermediate phase, ε-Fe2O3, during the magnetite maturation process in MTB via kinetic analysis. Unlike α-Fe2O3, which has been reported as a precursor during magnetosome biosynthesis in MTB before, ε-Fe2O3, due to its thermal instability, is a rare phase with scarce natural abundance. This finding confirmed that ε-Fe2O3 is an important novel intermediate during the biomineralization of magnetosome in MTB, and shed new light on the magnetosome biosynthesis pathway.

Highlights

Magnetite nano-particles are widely distributed mineral compounds found in various organisms including bacteria, bees, pigeons or even in human beings [1,2,3,4]
Unlike α-Fe2O3, which has been reported as a precursor during magnetosome biosynthesis in Magnetotactic bacteria (MTB) before, ε-Fe2O3, due to its thermal instability, is a rare phase with scarce natural abundance
This finding confirmed that ε-Fe2O3 is an important novel intermediate during the biomineralization of magnetosome in MTB, and shed new light on the magnetosome biosynthesis pathway

Summary

Introduction

Magnetite nano-particles are widely distributed mineral compounds found in various organisms including bacteria, bees, pigeons or even in human beings [1,2,3,4]. Membrane-enveloped magnetite, biosynthesized by magnetotactic bacteria (MTB), is referred to as magnetosomes [5, 6]. Magnetosomes have great potential in bioengineering and biomedicine applications [7,8,9], the intracellular biomineralization mechanism of magnetosomes remains poorly understood. Since the discovery of MTB, it has been believed to be an optimal material for the study of biogenic magnetite biomineralization because of the simple structure of these organisms. In most MTB, the magnetosomes are composed of magnetic magnetite (Fe3O4) or sulfide greigite (Fe3S4) [10, 11] enveloped by biological membrane [12]. Magnetotactic bacteria (MTB) is considered one of the most abundant species around the world which can form intracellular membrane enveloped magnetic nanoparticles, referred to as magnetosomes. Though the biosynthesis of magnetosome represents a general biomineralization mechanism of biogenic magnetite, knowledge of magnetosome biosynthesis and biomineralization remains very limited

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Results

Discussion

Conclusion