Single-molecule imaging on living bacterial cell surface by high-speed AFM

Area of Science:

• Microscopy
• Bacterial cell biology
• Structural biology

Background:

• Electron and optical microscopy offer limited insights into live single-molecule dynamics.
• Existing techniques cannot visualize high-resolution structural dynamics of single molecules in living cells.

Purpose of the Study:

• To image and analyze the molecular dynamics of living bacterial cell surfaces using high-speed atomic force microscopy (HS-AFM).
• To characterize the structure and dynamics of the bacterial outer membrane at sub-molecular resolution in a near-native state.

Main Methods:

• Utilized high-speed atomic force microscopy (HS-AFM) to image magnetotactic bacterial cells in liquid medium.
• Anchored bacterial cells on a substrate modified with poly-L-lysine and glutaraldehyde.
• Employed nano-dissection to identify structural components.

Main Results:

• HS-AFM provided high-resolution images of live bacterial cell surfaces, revealing a net-like structure with holes.
• Observed dynamic diffusion of the holes within the net-like structure on the cell surface.
• Nano-dissection identified porin trimers as the constituents of this dynamic surface structure.

Conclusions:

• HS-AFM enables direct observation of dynamic molecular architectures on live cell surfaces.
• The bacterial outer membrane possesses a dynamic, porous, net-like structure primarily composed of porin trimers.
• This study pioneers the visualization of live bacterial surface molecular dynamics at high resolution.