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Bullet‐Shaped Magnetite Biomineralization Within a Magnetotactic Deltaproteobacterium: Implications for Magnetofossil Identification
Journal of Geophysical Research: Biogeosciences ( IF 3.7 ) Pub Date : 2020-06-30 , DOI: 10.1029/2020jg005680
Jinhua Li 1, 2, 3 , Nicolas Menguy 3, 4 , Andrew P. Roberts 5 , Lin Gu 6 , Eric Leroy 7 , Julie Bourgon 7 , Xin’an Yang 6 , Xiang Zhao 5 , Peiyu Liu 1, 2, 3, 8 , Hitesh G. Changela 1 , Yongxin Pan 1, 3, 8
Affiliation  

Magnetite produced by magnetotactic bacteria (MTB) provides stable paleomagnetic signals because it occurs as natural single‐domain magnetic nanocrystals. MTB can also provide useful paleoenvironmental information because their crystal morphologies are associated with particular bacterial groups and the environments in which they live. However, identification of the fossil remains of MTB (i.e., magnetofossils) from ancient sediments or rocks is challenging because of their generally small sizes and because the growth, morphology, and chain assembly of magnetite within MTB are not well understood. Nanoscale characterization is, therefore, needed to understand magnetite biomineralization and to develop magnetofossils as biogeochemical proxies for paleoenvironmental reconstructions. Using advanced transmission electron microscopy, we investigated magnetite growth and chain arrangements within magnetotactic Deltaproteobacteria strain WYHR‐1, which reveals how the magnetite grows to form elongated, bullet‐shaped nanocrystals. Three crystal growth stages are recognized: (i) initial isotropic growth to produce nearly round ~20 nm particles, (ii) subsequent anisotropic growth along the [001] crystallographic direction to ~75 nm lengths and ~30–40 nm widths, and (iii) unidirectional growth along the [001] direction to ~180 nm lengths, with some growing to ~280 nm. Crystal growth and habit differ from that of magnetite produced by other known MTB strains, which indicates species‐specific biomineralization. These findings suggest that magnetite biomineralization might be much more diverse among MTB than previously thought. When characterized adequately at species level, magnetofossil crystallography, and apomorphic features are, therefore, likely to become useful proxies for ancient MTB taxonomic groups or species and for interpreting the environments in which they lived.

中文翻译:

趋磁三角洲变形杆菌内的子弹形磁铁矿化:对磁化石鉴定的影响

趋磁细菌(MTB)产生的磁铁矿提供稳定的古磁信号,因为它是天然的单畴磁性纳米晶体。MTB还可以提供有用的古环境信息,因为它们的晶体形态与特定的细菌群和它们所生活的环境有关。然而,从古沉积物或岩石中鉴别出MTB的化石残留物(即磁化石)是具有挑战性的,因为它们的尺寸通常很小,并且由于对MTB中磁铁矿的生长,形态和链组装的了解还不够。因此,需要纳米级表征来了解磁铁矿的生物矿化并开发磁化石作为古地球重建的生物地球化学代理。使用先进的透射电子显微镜,我们研究了趋磁Deltaproteobacteria菌株WYHR-1中的磁铁矿生长和链排列,该菌株揭示了磁铁矿如何生长以形成细长的子弹形纳米晶体。认识到三个晶体生长阶段:(i)初始各向同性生长以产生接近圆形的〜20 nm粒子;(ii)随后沿[001]晶体学方向各向异性生长,直至〜75 nm的长度和〜30–40 nm的宽度,和( iii)沿[001]方向单向生长到〜180 nm的长度,有些生长到〜280 nm。晶体的生长和习性与其他已知MTB菌株产生的磁铁矿不同,这表明物种特异性生物矿化。这些发现表明,MTB中磁铁矿的生物矿化可能比以前认为的要多样化得多。当在物种层面充分表征时,
更新日期:2020-07-25
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