Ultrastructure of the Corynebacterium glutamicum cell wall

The cell wall structure of the Gram-positive Corynebacterium glutamicum was evaluated by electron microscopy of thin sections after freeze-substitution and conventional fixation with glutaraldehyde. For the cell wall an overall thickness of approximately 32 nm was determined, with 8.5 nm corresponding to an outer layer, 6.5 nm to an electron translucent region (ETR) as found in mycobacteria and 17 nm to the peptidoglycan. Knob-like surface structures previously observed in freeze-fracture experiments were detected when cells were conventionally processed with a fixation using glutaraldehyde. By mild treatment with detergents approximately 20 proteins were extracted from the cell wall. From seven of these N-terminal amino acid sequences were determined.