Quantitative Imaging of Single Unstained Magnetotactic Bacteria by Coherent X‑ray Diffraction Microscopy

Novel coherent diffraction microscopy provides a powerful lensless imaging method to obtain a better understanding of the microorganism at the nanoscale. Here we demonstrated quantitative imaging of intact unstained magnetotactic bacteria using coherent X-ray diffraction microscopy combined with an iterative phase retrieval algorithm. Although the signal-to-noise ratio of the X-ray diffraction pattern from single magnetotactic bacterium is weak due to low-scattering ability of biomaterials, an 18.6 nm half-period resolution of reconstructed image was achieved by using a hybrid input-output phase retrieval algorithm. On the basis of the quantitative reconstructed images, the morphology and some intracellular structures, such as nucleoid, polyβ-hydroxybutyrate granules, and magnetosomes, were identified, which were also confirmed by scanning electron microscopy and energy dispersive spectroscopy. With the benefit from the quantifiability of coherent diffraction imaging, for the first time to our knowledge, an average density of magnetotactic bacteria was calculated to be ∼1.19 g/cm³. This technique has a wide range of applications, especially in quantitative imaging of low-scattering biomaterials and multicomponent materials at nanoscale resolution. Combined with the cryogenic technique or X-ray free electron lasers, the method could image cells in a hydrated condition, which helps to maintain their natural structure

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3D rendering of a blood capillary

Map of the Shang Dynasty and location of Daxinzhuang.

<p>Both Yin Ruins and Daxinzhuang sites are marked in the map. Reprinted from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174057#pone.0174057.ref011" target="_blank">11</a>] under a CC BY license, with permission from [Lamassu Design], original copyright [2009].</p

Different views of the casting mold sherd.

<p>(A-F) Six faces of the casting mold sherd.</p

EDS results of the elemental analysis of the casting mold sherd.

<p>EDS results of the elemental analysis of the casting mold sherd.</p

AMS-¹⁴C dating of archaeological pig bone.

<p>AMS-¹⁴C dating of archaeological pig bone.</p

X-ray fluorescence mapping of copper and iron mapping in front decoration and back groove.

<p>(A) A groove is labelled by a white rectangle on the back of the casting mold sherd. One red dashed line indicates the deepest position in the groove. (B) X-ray fluorescence mapping of the copper on the back and a white dashed line encircles the groove. (C) X-ray fluorescence mapping of the iron on the back and a black dashed line encircles the groove. One side of the deepest line shows a gathering of iron, and on the other side, this reverses. (D) A probing range is labelled by a white rectangle on the front of the casting mold sherd. (E), (F) X-ray fluorescence mapping on the front decoration of copper and iron, respectively. Both elements have an uneven distribution and some correspondence to the profile of decorated patterns.</p