Wen Tong, Zhang Yunpeng, Geng Yuanyuan, Liu Junquan, Basit Abdul, Tian Jiesheng, Li Ying, Li Jilun, Ju Jing, Jiang Wei
1State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, 100193 People's Republic of China.
Department of Biology Science and Technology, Baotou Teacher's College, Baotou, 014030 People's Republic of China.
Biomater Res. 2019 Aug 2;23:13. doi: 10.1186/s40824-019-0162-1. eCollection 2019.
Natural 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, -FeO and ferrihydrite. Though the biosynthesis of magnetosome represents a general biomineralization mechanism of biogenic magnetite, knowledge of magnetosome biosynthesis and biomineralization remains very limited.
Cells 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.
In this study, we identified a novel intermediate phase, -FeO, during the magnetite maturation process in MTB via kinetic analysis. Unlike -FeO, which has been reported as a precursor during magnetosome biosynthesis in MTB before, -FeO, due to its thermal instability, is a rare phase with scarce natural abundance. This finding confirmed that -FeO is an important novel intermediate during the biomineralization of magnetosome in MTB, and shed new light on the magnetosome biosynthesis pathway.
天然生物磁铁矿纳米颗粒广泛分布于从微生物到人类的各种生物中。已发现其在生物体中非常重要，尤其是在导航方面。此外，纯化的磁铁矿纳米颗粒在生物工程和生物医学中也具有潜在应用。趋磁细菌（MTB）被认为是世界上最丰富的物种之一，它能形成细胞内膜包裹的磁性纳米颗粒，即磁小体。据我们所知，MTB中磁小体的生物矿化涉及一系列位于一个名为磁小体岛的大型不稳定基因组区域上的基因，该区域专门存在于MTB中。磁小体的磁铁矿核心通过Fe（III）离子中间体形成，例如-FeO和水铁矿。尽管磁小体的生物合成代表了生物源磁铁矿的一般生物矿化机制，但关于磁小体生物合成和生物矿化的知识仍然非常有限。
本研究中使用的细胞在7.5升生物反应器中培养，在磁小体生物合成条件产生后的每个特定时间间隔采集用于中间捕获的样品。使用高分辨率透射电子显微镜分析磁小体的详细结构。通过快速傅里叶变换分析获得晶体结构的参数。
在本研究中，我们通过动力学分析在MTB的磁铁矿成熟过程中鉴定出一种新的中间相-FeO。与之前报道的作为MTB磁小体生物合成前体的-FeO不同，-FeO由于其热不稳定性而在自然丰度中是一种罕见的相。这一发现证实了-FeO是MTB磁小体生物矿化过程中的一种重要新中间相，并为磁小体生物合成途径提供了新的线索。
