Freeze-fracture observations of Corynebacterium glutamicum: the occurrence of an outer membrane-like structure and the influence of temperature on the cytoplasmic membrane.

In order to elucidate temperature-dependent morphological changes in the cell envelope of the Gram-positive L-lysine-overproducing Corynebacterium glutamicum 9366 we carried out freeze-fracture investigations of native cells and studied their fatty acid composition. In addition to the cytoplasmic membrane C. glutamicum possesses at the periphery of the cell an additional fracture plane which is unusual in Gram-positive bacteria and is designated here as outer membrane-like structure. The fracture faces of this layer display a distinguishable appearance in several regions of the cell. Bacteria grown at various temperatures showed changes in the relation of the saturated to unsaturated fatty acids. We demonstrated that the cytoplasmic membrane was affected by these changes in the fatty acid composition.