Comparative ultrastructure of Mycobacterium leprae and Mycobacterium lepraemurium cell envelopes.

The structural properties of the cell envelopes of Mycobacterium leprae and Mycobacterium lepraemurium were investigated by freeze-fracture, freeze-etching, and negative-staining techniques. Freeze-fracture split the cell wall and exposed the internal features of the peptidoglycolipid mycosidic filamentous network. The cell membrane was also split into two asymmetric faces. The external fracture face was characterized by linear arrays of intramembranous particles, whereas the protoplasmic fracture face showed randomly distributed clusters of particulate entities. Comparative analysis of the ultrastructural features observed in M. leprae and M. lepraemurium indicated that the organization of the cell envelope in these two species differed particularly with respect to the amount and complexity of the superficial peptidoglycolipid and mycosidic integument, which is poorly developed in the mycobacterium responsible for human disease.

Correlation between the mobility of inner plasma membrane structure and agglutination by concanavalin A in two cell lines of MOPC 173 plasmocytoma cells.

Both the distribution of the concanavalin A-binding sites and the rearrangement of the intramembranous particles revealed by the freeze-etching technique, have been studied by means of two variants of the same cell line issued from MOPC 173 murine plasmocytoma. One variant does not agglutinate even in presence of high lectin concentration. It has been shown that the number of binding sites and affinity are almost the same in the two variants. The clustered distribution of intramembranous particles is induced by the interaction of the concanavalin A and the cell surface only in the variant which is agglutinable. From these results it became apparent that the clustered distribution of the membrane particulate components is an acquired feature of the plasma membrane accompanying cell agglutination.