The detection of magnetotactic bacteria and magnetofossils by means of magnetic anisotropy

Gehring, A. U.; Kind, Jessica; Charilaou, Michalis; García-Rubio, Inés

doi:10.1016/j.epsl.2011.06.024

Cited by 38 publications

(48 citation statements)

References 32 publications

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“…FMR spectroscopy is a nondestructive magnetofossil detection method that is sensitive to the net magnetic anisotropy resulting from factors such as particle size, shape, arrangement, composition and magnetostatic interactions. Its utility in magnetofossil detection is based on the observation that FMR spectra of intact magnetite single-chains from cultured MTB exhibit a number of distinguishing properties: multiple low-field absorption peaks in the derivative spectra and extracted empirical parameters from the integrated spectra that fall within a small range of values [20][21][22]24,25,37 demarcated by the dashed lines in Fig. 4a,b: effective g-factor g eff o2.12, asymmetry ratio Ao1 and ao0.25.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, for magnetofossils to serve as a marker of paleoredox conditions, there must be accurate ways of detecting them in the geological records and an understanding of how diagenesis affects their concentration in sediments. Magnetofossil detection methods employing magnetic property measurements in use today are largely based on characterizations of MTB isolated in pure culture known to produce linear chains of magnetite (Fe 3 O 4 ) magnetosomes [18][19][20][21][22][23][24][25][26] . Mechanistically, these methods are founded on the low-temperature crystallographic transition specific to single-magnetic domain magnetite 18 , pronounced uniaxial magnetic anisotropy that arises from the magnetosome chain architecture [20][21][22][23][24][25][26][27][28] and the uniformity in magnetosome size 19 .…”

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confidence: 99%

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Magnetic properties of uncultivated magnetotactic bacteria and their contribution to a stratified estuary iron cycle

et al. 2014

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Of the two nanocrystal (magnetosome) compositions biosynthesized by magnetotactic bacteria (MTB), the magnetic properties of magnetite magnetosomes have been extensively studied using widely available cultures, while those of greigite magnetosomes remain poorly known. Here we have collected uncultivated magnetite-and greigite-producing MTB to determine their magnetic coercivity distribution and ferromagnetic resonance (FMR) spectra and to assess the MTB-associated iron flux. We find that compared with magnetite-producing MTB cultures, FMR spectra of uncultivated MTB are characterized by a wider empirical parameter range, thus complicating the use of FMR for fossilized magnetosome (magnetofossil) detection. Furthermore, in stark contrast to putative Neogene greigite magnetofossil records, the coercivity distributions for greigite-producing MTB are fundamentally left-skewed with a lower median. Lastly, a comparison between the MTB-associated iron flux in the investigated estuary and the pyritic-Fe flux in the Black Sea suggests MTB play an important, but heretofore overlooked role in euxinic marine system iron cycle.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Magnetic properties of uncultivated magnetotactic bacteria and their contribution to a stratified estuary iron cycle

et al. 2014

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“…For the quantification of the magnetic anisotropy in MTB, we used FMR spectroscopy, which is a powerful technique for measuring anisotropy fields related to the shape of the particle and the arrangement of the set of particles (23,28). In FMR experiments, the precessional motion (Larmor precession) of the magnetization in an external magnetic field is enhanced by a perpendicularly incoming microwave field when the microwave frequency matches the Larmor frequency of the system (resonance).…”

Section: Fmr Experimentsmentioning

confidence: 99%

Anisotropy of Bullet-Shaped Magnetite Nanoparticles in the Magnetotactic Bacteria Desulfovibrio magneticus sp. Strain RS-1

Chariaou

Rahn-Lee

Kind

et al. 2015

Biophysical Journal

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Magnetotactic bacteria (MTB) build magnetic nanoparticles in chain configuration to generate a permanent dipole in their cells as a tool to sense the Earth's magnetic field for navigation toward favorable habitats. The majority of known MTB align their nanoparticles along the magnetic easy axes so that the directions of the uniaxial symmetry and of the magnetocrystalline anisotropy coincide. Desulfovibrio magneticus sp. strain RS-1 forms bullet-shaped magnetite nanoparticles aligned along their (100) magnetocrystalline hard axis, a configuration energetically unfavorable for formation of strong dipoles. We used ferromagnetic resonance spectroscopy to quantitatively determine the magnetocrystalline and uniaxial anisotropy fields of the magnetic assemblies as indicators for a cellular dipole with stable direction in strain RS-1. Experimental and simulated ferromagnetic resonance spectral data indicate that the negative effect of the configuration is balanced by the bullet-shaped morphology of the nanoparticles, which generates a pronounced uniaxial anisotropy field in each magnetosome. The quantitative comparison with anisotropy fields of Magnetospirillum gryphiswaldense, a model MTB with equidimensional magnetite particles aligned along their (111) magnetic easy axes in well-organized chain assemblies, shows that the effectiveness of the dipole is similar to that in RS-1. From a physical perspective, this could be a reason for the persistency of bullet-shaped magnetosomes during the evolutionary development of magnetotaxis in MTB.

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“…For S-band experiments, cultured cells of M. gryphiswaldense strain MSR-1 were used in the earlier studies [11,30,31]. The MTB were cultured following the procedure by Heyen & Schü ler [38].…”

Section: Experimental Set-upmentioning

confidence: 99%

“…asymmetry of the absorption spectra) permit a direct way to detect the anisotropy of magnetosome chains [11,[27][28][29][30][31][32]. Mastrogiacomo et al [33] showed that FMR experiments of MTB using microwave frequency of 4 GHz, i.e.…”

Section: Introductionmentioning

confidence: 99%

S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils

Gehring

Kind

Charilaou

et al. 2013

J. R. Soc. Interface.

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We report the use of S-band ferromagnetic resonance (FMR) spectroscopy to compare the anisotropic properties of magnetite particles in chains of cultured intact magnetotactic bacteria (MTB) between 300 and 15 K with those of sediment samples of Holocene age in order to infer the presence of magnetofossils and their preservation in a geological time frame. The spectrum of intact MTB at 300 K exhibits distinct uniaxial anisotropy because of the chain alignment of the cellular magnetite particles and their easy axes. This anisotropy becomes less pronounced upon cooling and below the Verwey transition (T V ) it is nearly vanished mainly owing to the change of direction of the easy axes. In a natural sample, magnetofossils were detected by uniaxial anisotropy traits similar to those obtained from cultured MTB above T V . Our comparative study emphasizes that indispensable information can be obtained from S-band FMR spectra, which offers even a better resolution than X-band FMR for discovering magnetofossils, and this in turn can contribute towards strengthening our relatively sparse database for deciphering the microbial ecology during the Earth's history.

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The detection of magnetotactic bacteria and magnetofossils by means of magnetic anisotropy

Cited by 38 publications

References 32 publications

Magnetic properties of uncultivated magnetotactic bacteria and their contribution to a stratified estuary iron cycle

Magnetic properties of uncultivated magnetotactic bacteria and their contribution to a stratified estuary iron cycle

Anisotropy of Bullet-Shaped Magnetite Nanoparticles in the Magnetotactic Bacteria Desulfovibrio magneticus sp. Strain RS-1

S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils

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