X-ray microtomographic visualization of Escherichia coli by metalloprotein overexpression

TL;DR

This study demonstrates that overexpressing metalloprotein ferritin in E. coli enables detailed 3D visualization of the bacteria using X-ray microtomography, revealing cellular structures with high contrast.

Contribution

It introduces a method for visualizing biological cells in 3D using metalloprotein overexpression combined with advanced X-ray imaging techniques.

Findings

Ferritin-expressing E. coli show homogeneous X-ray absorption.

Cells exhibit absorption similar to phosphotungstic-acid stained samples.

Submicrometer structures are visualized with phase contrast imaging.

Abstract

This paper reports X-ray microtomographic visualization of the microorganism Escherichia coli overexpressing a metalloprotein ferritin. The three-dimensional distribution of linear absorption coefficients determined using a synchrotron radiation microtomograph with a simple projection geometry revealed that the X-ray absorption was homogeneously distributed, suggesting that every E. coli cell was labeled with the ferritin. The ferritin-expressing E. coli exhibited linear absorption coefficients comparable to those of phosphotungstic-acid stained cells. The submicrometer structure of the ferritin-expressing E. coli cells was visualized by Zernike phase contrast using an imaging microtomograph equipped with a Fresnel zone plate. The obtained images revealed curved columnar or bunching oval structures corresponding to the E. coli cells. These results indicate that the metalloprotein overexpression facilitates X-ray visualization of three-dimensional cellular structures of biological objects.