Attachment and short-term maintenance of motility and viability of Entamoeba histolytica in a defined medium.

Organic requirements for attachment to glass, elongation, and motility of Entamoeba histolytica, have been determined. The trophozoite, which has been grown axenically only in highly complex media with reduced oxygen tensions, remains rounded and detached when placed in a Tris-HCl buffered solution containing NaCl, KCl, MgClI, and CaCl2. A maintenance medium in which the amebae could attach to glass, elongate, and remain motile and viable for 12 to 24 h was devised with the addition of cysteine, ascorbic acid, bovine serum albumin, and the vitamin solution of medium NCTC No. 107. Tris-HCl was the most effective buffer tested and the optimal pH was 6.9 to 7.0. Survival, but attachment, of the amebae was decreased at osmolalities ranging between 110 and 180 milliosmoles/kg, whereas both functions were decreased above approximately 260 milliosmoles/kg. Bovine serum albumin, the most effective of the proteins tested, and the vitamin solution helped maintain attachment of some ameba strains, but were not required by other strains. The requirements for cysteine and ascorbic acid were absolute and highly specific. During incubation in the maintenance medium, cell volumes decreased. Sensitivity of the organisms to agglutination by concanavalin A, wheat germ agglutinin, soybean agglutinin and fucose binding protein remained unchanged.