Chemical signature of magnetotactic bacteria

Matthieu F Amor (1, 2) , Vincent F Busigny (1) , Mickaël F Durand-Dubief (3) , Mickaël F Tharaud (4, 1) , Georges F Ona-Nguema (5) , Alexandre F Gélabert (1) , Edouard F Alphandéry (2, 3) , Nicolas F Menguy (5) , Marc F Benedetti (1) , Imène F Chebbi (3) , François F Guyot (5)

1 IPGP - Institut de Physique du Globe de Paris
2 IMPMC - Institut de minéralogie et de physique des milieux condensés
3 Nanobactérie SARL
4 IPGP - Institut de Physique du Globe de Paris
5 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie

There are longstanding and ongoing controversies about the abiotic or biological origin of nanocrystals of magnetite. On Earth, magne-totactic bacteria perform biomineralization of intracellular magne-tite 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. magnetotactic bacteria | magnetite | biomineralization | trace element incorporation

Mots clés: magnetotactic bacteria; magnetite; biomineralization; trace element incorporation

Domaines: Planète et Univers [physics]

Matthieu F Amor, Vincent F Busigny, Mickaël F Durand-Dubief, Mickaël F Tharaud, Georges F Ona-Nguema, et al.. Chemical signature of magnetotactic bacteria. Proceedings of the National Academy of Sciences of the United States of America, 2014, 112, pp.1699 - 1703. ⟨10.1073/pnas.1414112112⟩. ⟨insu-01446706⟩