title: High resolution CryoFESEM of microbial surfaces.
abstract: 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.
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota Medical School, Minneapolis, MN 55455, USA. erlan001@umn.edu
authors.forename: Stanley
authors.initials: S
authors.lastname: Erlandsen
authors.forename: Ming
authors.initials: M
authors.lastname: Lei
authors.forename: Ines
authors.initials: I
authors.lastname: Martin-Lacave
authors.forename: Gary
authors.initials: G
authors.lastname: Dunny
authors.forename: Carol
authors.initials: C
authors.lastname: Wells
mesh_terms: 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*