The detection of magnetotactic bacteria and magnetofossils by means of magnetic anisotropy
Abstract
An important characteristic of magnetotactic bacteria (MTB) is the anisotropy of one-dimensionally aligned magnetite particles. This paper introduces the use of ferromagnetic resonance spectroscopy (FMR) at two different frequencies to compare the anisotropic properties of magnetite chains of cultured intact MTB with those of lake sediments of Holocene age in order to detect magnetofossils and to characterize their preservation in a geological system. Magnetite chains of intact MTB exhibit a predominantly uniaxial anisotropy. In the lake sediments, where diagenetic processes disintegrate the chains and diminish their uniaxiality, magnetite chains or chain fragments and dissociated bulk magnetite particles differ in their anisotropy properties. The two groups of assembly can be distinguished by empirical spectral separation of the FMR signal. This straightforward use of the characteristics of magnetic anisotropy provides a way to detect magnetofossils experimentally, thus allowing a better insight into microbial ecology during Earth's history.
- Publication:
-
Earth and Planetary Science Letters
- Pub Date:
- September 2011
- DOI:
- 10.1016/j.epsl.2011.06.024
- Bibcode:
- 2011E&PSL.309..113G
- Keywords:
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- ferromagnetic resonance spectroscopy (FMR);
- Magnetospirillum gryphiswaldense;
- lake sediments;
- assembly of magnetosomes;
- cellular dipole;
- chain fragments