Amor Matthieu, Busigny Vincent, Durand-Dubief Mickaël, Tharaud Mickaël, Ona-Nguema Georges, Gélabert Alexandre, Alphandéry Edouard, Menguy Nicolas, Benedetti Marc F, Chebbi Imène, Guyot François
Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, 75238 Paris, France; Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Universités, Université Pierre et Marie Curie, UMR 7590 CNRS, Institut de Recherche pour le Développement UMR 206, Museum National d'Histoire Naturelle, 75252 Paris Cedex 05, France; and
Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, 75238 Paris, France;
Proc Natl Acad Sci U S A. 2015 Feb 10;112(6):1699-703. doi: 10.1073/pnas.1414112112. Epub 2015 Jan 26.
There are longstanding and ongoing controversies about the abiotic or biological origin of nanocrystals of magnetite. On Earth, magnetotactic bacteria perform biomineralization of intracellular magnetite nanoparticles under a controlled pathway. These bacteria are ubiquitous in modern natural environments. However, their identification in ancient geological material remains challenging. Together with physical and mineralogical properties, the chemical composition of magnetite was proposed as a promising tracer for bacterial magnetofossil identification, but this had never been explored quantitatively and systematically for many trace elements. Here, we determine the incorporation of 34 trace elements in magnetite in both cases of abiotic aqueous precipitation and of production by the magnetotactic bacterium Magnetospirillum magneticum strain AMB-1. We show that, in biomagnetite, most elements are at least 100 times less concentrated than in abiotic magnetite and we provide a quantitative pattern of this depletion. Furthermore, we propose a previously unidentified method based on strontium and calcium incorporation to identify magnetite produced by magnetotactic bacteria in the geological record.
关于磁铁矿纳米晶体的非生物或生物起源，存在长期且持续的争议。在地球上，趋磁细菌在可控途径下进行细胞内磁铁矿纳米颗粒的生物矿化。这些细菌在现代自然环境中无处不在。然而，在古代地质材料中识别它们仍然具有挑战性。除了物理和矿物学性质外，磁铁矿的化学成分被认为是识别细菌磁化石的一个有前景的指标，但对于许多微量元素，从未进行过定量和系统的研究。在这里，我们确定了在非生物水沉淀和趋磁细菌磁螺菌AMB-1产生磁铁矿这两种情况下34种微量元素在磁铁矿中的掺入情况。我们表明，在生物磁铁矿中，大多数元素的浓度至少比非生物磁铁矿低100倍，并且我们提供了这种贫化的定量模式。此外，我们提出了一种基于锶和钙掺入的先前未被识别的方法，以识别地质记录中由趋磁细菌产生的磁铁矿。
