Morphology visualization of irregular shape bacteria by electron holography and tomography

Area of Science:

• Microbiology
• Nanotechnology
• Electron Microscopy

Background:

• Staphylococcus aureus is a significant human pathogen.
• Understanding bacterial morphology and nanoparticle interactions is crucial for developing new antimicrobial strategies.
• Conventional imaging techniques can be time-consuming and cause radiation damage to delicate biological samples.

Purpose of the Study:

• To visualize the irregular morphology of Staphylococcus aureus bacteria.
• To investigate the interaction of gold nanoparticles (AuNP) with Staphylococcus aureus.
• To evaluate the efficacy of off-axis electron holography (EH) as an advanced imaging technique.

Main Methods:

• Phase retrieval using off-axis electron holography (EH).
• 3D reconstruction electron tomography using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM).
• Imaging of Staphylococcus aureus interacting with gold nanoparticles (AuNP).

Main Results:

• Air dehydration processing induced shrunken or irregular shapes in bacteria.
• HAADF-STEM imaging confirmed AuNP attachment to bacterial surfaces.
• Off-axis electron holography (EH) successfully revealed bacterial morphology and AuNP distribution from a single hologram.
• EH significantly reduced acquisition time and radiation damage by three orders of magnitude compared to electron tomography.
• EH also decreased processing time and reconstruction artifacts.

Conclusions:

• Off-axis electron holography (EH) is a powerful tool for visualizing bacterial morphology and nanoparticle distribution.
• EH offers a faster and less damaging alternative to conventional electron tomography for biological imaging.
• This technique has potential applications in studying nanoparticle-bacteria interactions and developing novel therapeutic approaches.