Individual filamentous phage imaged by electron holography

Area of Science:

• Electron microscopy
• Structural biology
• Biophysics

Background:

• Accurate imaging of individual biological molecules is crucial for understanding their structure and function.
• Traditional electron microscopy techniques can be limited by sample preparation and radiation damage.

Purpose of the Study:

• To demonstrate the feasibility of using a low energy electron point source (LEEPS) microscope for in-line electron holography of individual bacteriophages.
• To reconstruct a numerical image of a phage particle from its electron hologram.

Main Methods:

• A custom-built LEEPS microscope was used with coherent low energy electrons (88 eV).
• Cryo-microscopy techniques were employed, including rapid freezing in amorphous ice and sublimation, to prepare individual, free-standing f1.K phages.
• In-line electron holograms were recorded and numerically reconstructed to obtain an amplitude image of the phage.

Main Results:

• An electron hologram of a single f1.K phage was successfully recorded.
• A numerical reconstruction yielded an image of the phage, magnified 100,000x, suspended across a slit in a carbon membrane.
• The reconstructed image dimensions and morphology were consistent with transmission electron microscopy (TEM) data.

Conclusions:

• It is possible to record and reconstruct electron holograms of individual bacteriophages using LEEPS microscopy.
• The method shows potential for structural studies of biological molecules, with future work focused on improving resolution.