Intracellular membrane structures of the mycoplasma-like organisms inducing carrot yellows.

Intracellular membrane structures from 16 to 22 nm wide were found in the mycoplasma-like organisms causing carrot yellows. These structures are composed of five layers, three electron-dense and two electron-transparent. The membrane structures are situated, as a rule, in the central nucleoid zone of the cells of the mycoplasma-like organisms and may be seen to be in direct contact with the DNA fibrils. Ribosomes may be seen around the membrane structures. In this work we show the morphological connection between the membrane structures and the external elementary membrane of the mycoplasma-like organisms and also invagination of the external membrane into the cell. It is proposed that the intracellular membrane structures arise by means of invagination of the external elementary membrane and form a single system with this. This is the first instance of discovery of intracellular membrane structures in mycoplasmata.