transmission electron microscopy was used by mauricio toro-nahuelpan to visualize the magnetosomes, as they are located inside the cell. however, which type of microscopy would work best if the magnetosomes were located on the outside of the cell?

For magnetosomes located on the outside of the cell, the best choice would be a surface‑sensitive technique such as scanning electron microscopy (SEM) or atomic force microscopy (AFM) , rather than transmission electron microscopy.

Why SEM or AFM works better here

• SEM
  • Designed to image surface topography at very high resolution.
  • Gives detailed 3D‑like views of particles or organelles attached to or protruding from the cell surface, making it ideal for extracellular magnetosomes.
  • Widely used to study nanoscale surface structures on cells and materials, because it scans the surface with an electron beam instead of transmitting electrons through a thin slice.
• AFM (a type of scanning probe microscopy)
  • Uses a nanometer‑scale tip that physically scans the specimen surface, producing a precise height map.
  • Particularly powerful for nanoscale surface structures like magnetosome chains or particles on the outer membrane, and can work in air or liquid.
  • Has been successfully used to visualize magnetosomes from magnetotactic bacteria as individual nanoparticles and chains on surfaces.

Putting it into a simple answer

If the magnetosomes are inside the cell → TEM is ideal, because it reveals internal ultrastructure by transmitting electrons through thin sections.
If the magnetosomes are outside the cell → SEM or AFM would work best, with SEM being the classic, widely taught answer for visualizing external surface structures and AFM being an equally powerful, more specialized alternative for high‑resolution surface imaging.