OSMOLARITY IS AN INDEPENDENT TRIGGER OF ACANTHAMOEBA-CASTELLANII DIFFERENTIATION

Like many yeasts, bacteria, and other sporulating microorganisms, Acan thamoeba castellanii (Neff), a free-living amoeba with pathogenic rela tives, differentiates into a dormant form when deprived of nutrients. Acanthamoeba cysts redifferentiate into trophozoites when food is resu pplied. We report here that Acanthamoeba encystment is also triggered by elevated osmolarity, and that osmolarity and cell surface receptor binding are synergistic in triggering differentiation. Additions of so dium chloride or glucose to rich growth media were used to produce spe cific osmolarity increases and similar encystment results were obtaine d with either additive. Although many organisms, including Acanthamoeb a and mammalian cells, have been shown to adapt to hyperosmolar condit ions, this is the first demonstration that hyperosmolarity can be a pr imary differentiation signal. (C) 1996 Wiley-Liss, Inc.