Related Experiment Video
Updated: Jul 25, 2026
05:57
Collection, Isolation and Enrichment of Naturally Occurring Magnetotactic Bacteria from the Environment
Published on: November 15, 2012
Magnetic microstructure of magnetotactic bacteria by electron holography
Dunin-Borkowski1, McCartney, Frankel
1R. E. Dunin-Borkowski and M. R. McCartney, Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704, USA. R. B. Frankel, Department of Physics, California Polytechnic State University, San Luis Obispo, CA 93407, USA. D.
Science (New York, N.Y.)
|December 4, 1998
Summary
Magnetotactic bacteria use magnetite nanocrystals for magnetic alignment. Electron holography revealed how crystal shape and interactions influence their magnetic properties, crucial for understanding bacterial navigation.
Area of Science:
- Biophysics
- Materials Science
- Microscopy
Background:
- Magnetotactic bacteria synthesize intracellular magnetite (Fe3O4) nanocrystals for geomagnetic field alignment.
- Understanding the interplay between physical structure and magnetic properties is key to their function.
- Previous studies often lacked direct correlation between individual crystal morphology and magnetic behavior.
Purpose of the Study:
- To correlate the physical and magnetic microstructure of magnetite nanocrystals within magnetotactic bacteria.
- To investigate the magnetic domain structure and anisotropy in these biogenic nanomagnets.
- To determine the magnetic interaction effects and coercive force in bacterial magnetite chains.
Main Methods:
- Utilized off-axis electron holography in a transmission electron microscope (TEM).
- Analyzed the physical morphology and magnetic microstructure of individual magnetite nanocrystals.
- Examined magnetic interactions between superparamagnetic and larger magnetite crystals in bacterial chains.
Main Results:
- All magnetite crystals were confirmed as single magnetic domains.
- Magnetization directions of small superparamagnetic crystals were influenced by magnetic interactions with larger crystals.
- Shape anisotropy was observed to be the dominant factor over magnetocrystalline anisotropy in elongated crystals.
- A coercive field ranging from 300 to 450 oersted was measured for a representative magnetite chain.
Conclusions:
- Off-axis electron holography provides a powerful tool for correlating physical and magnetic properties at the nanoscale in biological systems.
- Magnetic interactions and shape anisotropy play significant roles in determining the magnetic behavior of magnetite chains in magnetotactic bacteria.
- These findings contribute to a deeper understanding of biomineralization and the principles of magnetic self-assembly in biological nanomaterials.
Related Concept Videos
01:25Overview of Electron Microscopy
The wavelengths of visible light ultimately limit the maximum theoretical resolution of images created by light microscopes. Most light microscopes can only magnify 1000X, and a few can magnify up to 1500X. Electrons, like electromagnetic radiation, can behave like waves, but with wavelengths of 0.005 nm, they produce significantly greater resolution up to 0.05 nm as compared to 500 nm for visible light. An electron microscope (EM) can create a sharp image that is magnified up to 2,000,000X.
01:15Transmission Electron Microscopy
In 1931, physicist Ernst Ruska—building on the idea that magnetic fields can direct an electron beam just as lenses can direct a beam of light in an optical microscope—developed the first prototype of the electron microscope. This development led to the development of the field of electron microscopy. In the transmission electron microscope (TEM), electrons are produced by a hot tungsten element and accelerated by a potential difference in an electron gun, which gives them up to 400 keV in...
01:29Two-Dimensional Microscopy in Microbiology
Two-dimensional (2D) microscopy encompasses a range of optical techniques that capture images within a single focal plane, offering detailed representations of microscopic structures. These techniques are essential in biological and medical research, enabling the visualization of cellular and subcellular structures with different levels of contrast and specificity.There are several major types of 2D microscopy, each with strengths and applications.Bright-Field MicroscopyBright-field microscopy...
01:28Three-Dimensional Microscopy in Microbiology
Three-dimensional imaging techniques are essential in cell biology, allowing researchers to visualize intricate cellular structures with high resolution. Two prominent methods, Differential Interference Contrast Microscopy (DIC) and Confocal Scanning Laser Microscopy (CSLM), provide distinct advantages for imaging live and thick specimens, respectively.Differential Interference Contrast MicroscopyDIC microscopy enhances contrast in transparent, unstained samples by converting phase...
01:13Special Staining Techniques
Specialized staining techniques play a vital role in microbiology by enabling the visualization of specific bacterial structures that remain undetectable with standard microscopy methods. These techniques not only enhance the structural visualization of bacterial cells but also provide critical insights into their pathogenicity and classification. Additionally, they support diagnostic and research endeavors in microbiology by identifying key bacterial features.Capsule Staining for Virulence...
01:18Other Unique Bacteria
Magnetic bacteria exhibit a directed movement called magnetotaxis, driven by structures called magnetosomes. These magnetosomes consist of chains of magnetic particles made of either magnetite (Fe₃O₄) or greigite (Fe₃S₄) and are organized in a linear conformation by a protein scaffold within invaginations of the cell membrane. The bacteria align along the north–south magnetic field lines, much like a compass needle. They are typically microaerophilic or anaerobic and are commonly found near the...