Measuring spectroscopy and magnetism of extracted and intracellular magnetosomes using soft X-ray ptychography

Abstract

Characterizing the chemistry and magnetism of magnetotactic bacteria (MTB) is an important aspect of understanding the biomineralization mechanism and function of the chains of magnetosomes (Fe 3 O 4 nanoparticles) found in such species. Images and X-ray absorption spectra (XAS) of magnetosomes extracted from, and magnetosomes in, whole Magnetovibrio blakemorei strain MV-1 cells have been recorded using soft X-ray ptychography at the Fe 2p edge. A spatial resolution of 7 nm is demonstrated. Precursor-like and immature magnetosome phases in a whole MV-1 cell were visualized, and their Fe 2p spectra were measured. Based on these results, a model for the pathway of magnetosome biomineralization for MV-1 is proposed. Fe 2p X-ray magnetic circular dichroism (XMCD) spectra have been derived from ptychography image sequences recorded using left and right circular polarization. The shape of the XAS and XMCD signals in the ptychographic absorption spectra of both sample types is identical to the shape and signals measured with conventional bright-field scanning transmission X-ray microscope. A weaker and inverted XMCD signal was observed in the ptychographic phase spectra of the extracted magnetosomes. The XMCD ptychographic phase spectrum of the intracellular magnetosomes differed from the ptychographic phase spectrum of the extracted magnetosomes. These results demonstrate that spectro-ptychography offers a superior means of characterizing the chemical and magnetic properties of MTB at the individual magnetosome level.ptychography | magnetotactic bacteria | biomineralization | STXM |

Bullet‐Shaped Magnetite Biomineralization Within a Magnetotactic Deltaproteobacterium: Implications for Magnetofossil Identification

“…Microscopic identifications of magnetofossils tend to rely on morphological recognition based on conventional TEM observations (Chang et al, 2018; Li, Benzerara, et al, 2013; Yamazaki et al, 2019), which fail to acquire detailed information on crystal growth and habit and sometimes result in magnetofossil misidentification (Buseck et al, 2001). Therefore, additional systematic studies of magnetosomal crystals in both modern MTB and magnetotactic eukaryotes, and magnetofossils from ancient sediments with various combined advanced TEM and STXM approaches are vital (Buseck et al, 2001; Kalirai et al, 2013; Leão et al, 2020; Li, Benzerara, et al, 2013; Zhu et al, 2016). In addition, studies of magnetosomal biomineralization in MTB grown in controlled laboratory conditions are still needed to expand our knowledge of the relationship between crystal growth and MTB phylogeny and/or environmental factors (Faivre et al, 2008; Lefèvre et al, 2016; Li et al, 2009; Li & Pan, 2012).…”

Radiação de Síncrotron no Brasil UVX e Sirius

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Tomographic reconstruction of a three-dimensional magnetization vector field

“…Although x-ray ptychography was used in the experimental demonstration of magnetic nanotomography in [9], x-ray ptychography is not required for the reconstruction of the magnetization, and magnetic tomography can be used with a number of different x-ray imaging techniques. Furthermore, in combination with lower energy soft x-rays [33], where the magnetic signal is significantly higher, high spatial resolution reconstructions of the three-dimensional magnetization within thin films and magnetic nanostructures with a spatial resolution below 10 nm are now feasible.…”