Periplasmic gel: new concept resulting from the reinvestigation of bacterial cell envelope ultrastructure by new methods

J Bacteriol. 1984 Oct;160(1):143-52. doi: 10.1128/jb.160.1.143-152.1984.

Abstract

Bacterial cell envelope ultrastructure was investigated both by the progressive lowering of temperature embedding technique and freeze-substitution, using conventional and scanning transmission electron microscopy. Comparison with standard embedding procedures revealed a new aspect of cell envelope structure in specimens at low temperatures. The envelope was delimited by an electron-dark layer, beneath which was a uniform matter-containing layer lying between the outer and inner membranes. There was no empty periplasmic space. Buoyant densities of isolated peptidoglycan obtained in Percoll (1.02 to 1.07 g ml-1) and CsCl2 (1.44 g ml-1) led to a calculated hydration of the peptidoglycan which was more than was previously assumed. Peptidoglycan therefore possibly fills the entire space between the inner and outer membranes in the form of a periplasmic gel. The new model of cell envelope organization is discussed with respect to the current knowledge on bacterial cell wall structure and function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriological Techniques
  • Cell Membrane / ultrastructure*
  • Escherichia coli / ultrastructure*
  • Freezing
  • Gels
  • Indicators and Reagents
  • Microscopy, Electron
  • Microscopy, Electron, Scanning
  • Peptidoglycan / analysis
  • Staining and Labeling

Substances

  • Gels
  • Indicators and Reagents
  • Peptidoglycan