Freeze-etching study of human and murine leprosy bacilli.

Morphologic features of the electron transparent zone (ETZ) material around human and murine leprosy bacilli were examined by a freeze-etching technic. The ETZ around human leprosy bacilli is composed of spherical droplets of hydrophobic material. These are always liquid at body temperature and they never show crystalline lamellar structure even at the temperature of liquid nitrogen. The ETZ around murine leprosy bacilli is composed of ribbon-like or membranous crystalline structures. This material is solid and crystalline at the body temperature of mice, and this solid material is the chief cause of the random arrangement of murine leprosy bacilli inside the cytoplasm of murine lepra cells. This crystalline structure has also been observed around murine leprosy bacilli grown on cell-free culture media.