Examining the chemistry and magnetism of magnetotactic bacterium Candidatus Magnetovibrio blakemorei strain MV-1 using scanning transmission X-ray microscopy

Scanning transmission X-ray microscopy (STXM) measurements at the C K, O K and Fe L3 edges were used to study the magnetotactic bacterium Candidatus Magnetovibrio blakemorei strain MV-1 on an individual cell basis. Improved data acquisition methodologies resulting in higher quality results are presented. Visualization of magnetosomes from their O K-edge signal is demonstrated. The Fe L3 X-ray magnetic circular dichroism (XMCD) signal was used to characterize the magnetic properties of several MV-1 cells on an individual magnetosome basis. The absolute magnetic moment from two cells was evaluated and found to be 0.93(6) of that of saturated abiotic magnetite, or 3.6(2) μB. Previously observed excess Fe (II) was not found in this study, suggesting the prior observation (Lam et al., Chem. Geol 270 (2010) 110) may have been a radiation damage artifact.

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► Improved experimental methods for acquiring STXM-XMCD are described.
► Improved data quality and reduction of artifacts in magnetosome studies are demonstrated.
► C 1s and O 1s studies of biological components of MV-1 cells are reported.
► XMCD of magnetosomes of two overlapping MV-1 cells show opposite alignment.
► Absolute magnetic moment averaged over two chains is 3.6(2) μB, 94(6)% of abiotic magnetite.