Ultrastructure of a magnetotactic spirillum

Area of Science:

• Microbiology
• Biophysics
• Cell Biology

Background:

• Magnetotactic bacteria exhibit unique intracellular structures enabling response to magnetic fields.
• Understanding the ultrastructure of these bacteria is crucial for elucidating their magnetoreception mechanisms.

Purpose of the Study:

• To investigate the ultrastructure of magnetotactic bacterium strain MS-1.
• To identify and characterize the nature of electron-dense particles responsible for magnetic properties.

Main Methods:

• Transmission electron microscopy (TEM)
• Scanning electron microscopy (SEM)
• Scanning-transmission electron microscopy (STEM)
• Energy-dispersive X-ray analysis (EDX)

Main Results:

• Strain MS-1 shares general morphology with other spirilla but possesses unique ultrastructural features.
• Electron-dense particles, confirmed by EDX to contain iron, form a consistent chain within magnetotactic cells.
• A non-magnetotactic variant of strain MS-1 lacks these iron-containing inclusion bodies.
• Each particle is enveloped by a distinct layer structure.

Conclusions:

• The term "magnetosome" is proposed for the iron-containing particles and their associated layers in magnetotactic bacteria.
• The specific arrangement and composition of magnetosomes are key to the bacterium's motility and orientation in magnetic fields.