Nanoscale imaging of bacterial infections by sphingolipid expansion microscopy

Nat Commun. 2020 Dec 2;11(1):6173. doi: 10.1038/s41467-020-19897-1.

Abstract

Expansion microscopy (ExM) enables super-resolution imaging of proteins and nucleic acids on conventional microscopes. However, imaging of details of the organization of lipid bilayers by light microscopy remains challenging. We introduce an unnatural short-chain azide- and amino-modified sphingolipid ceramide, which upon incorporation into membranes can be labeled by click chemistry and linked into hydrogels, followed by 4× to 10× expansion. Confocal and structured illumination microscopy (SIM) enable imaging of sphingolipids and their interactions with proteins in the plasma membrane and membrane of intracellular organelles with a spatial resolution of 10-20 nm. As our functionalized sphingolipids accumulate efficiently in pathogens, we use sphingolipid ExM to investigate bacterial infections of human HeLa229 cells by Neisseria gonorrhoeae, Chlamydia trachomatis and Simkania negevensis with a resolution so far only provided by electron microscopy. In particular, sphingolipid ExM allows us to visualize the inner and outer membrane of intracellular bacteria and determine their distance to 27.6 ± 7.7 nm.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cell Membrane / metabolism
  • Cell Membrane / ultrastructure
  • Ceramides / chemistry*
  • Ceramides / metabolism
  • Chlamydia trachomatis / metabolism
  • Chlamydia trachomatis / ultrastructure*
  • Chlamydiales / metabolism
  • Chlamydiales / ultrastructure*
  • Click Chemistry / methods
  • Conjunctiva / cytology
  • Epithelial Cells / metabolism
  • Epithelial Cells / microbiology
  • Epithelial Cells / ultrastructure*
  • HeLa Cells
  • Humans
  • Hydrogels / chemistry
  • Intracellular Membranes / metabolism
  • Intracellular Membranes / ultrastructure
  • Microscopy, Confocal / methods*
  • Microscopy, Fluorescence / methods*
  • Neisseria gonorrhoeae / metabolism
  • Neisseria gonorrhoeae / ultrastructure*
  • Staining and Labeling / methods

Substances

  • Ceramides
  • Hydrogels
  • omega-amino-ceramide

Supplementary concepts

  • Simkania negevensis

Associated data

  • figshare/10.6084/m9.figshare.13147955