High resolution CryoFESEM of microbial surfaces.
The outer surfaces of three microorganisms, Giardia lamblia, Enterococcus faecalis, and Proteus mirabilis, were investigated by cryo-immobilization followed by sublimation of extracellular ice and cryocoating with either Pt alone or Pt plus carbon. Cryocoated samples were examined at -125 degrees C in either an in-lens field emission SEM or a below-the-lens field emission SEM. Cryocoating with Pt alone was sufficient for low magnification observation, but attempts to do high-resolution imaging resulted in radiolysis and cracking of the specimen surface. Double coating with Pt and carbon, in combination with high resolution backscatter electron detectors, enabled high-resolution imaging of the glycocalyx of bacteria, revealing a sponge-like network over the surface. High resolution examination of bacterial flagella also revealed a periodic substructure. Common artifacts included radiolysis leading to "cracking" of the surface, and insufficient deposition of Pt resulting in the absence of detectable surface topography.
Erlandsen
Stanley
S
Department of Genetics, Cell Biology and Development, University of Minnesota Medical School, Minneapolis, MN 55455, USA. erlan001@umn.edu
Lei
Ming
M
Martin-Lacave
Ines
I
Dunny
Gary
G
Wells
Carol
C
D000818:Animals; D020285:Cryoelectron Microscopy / Q000379:methods*; D013293:Enterococcus faecalis / Q000648:ultrastructure*; D005872:Giardia / Q000648:ultrastructure*; D019276:Glycocalyx / Q000648:ultrastructure*; D011513:Proteus mirabilis / Q000648:ultrastructure*