Extrinsic requirements for encystation by soil amoeba, Hartmannella rhysodes.

SYNOPSIS. The environmental factors causing encystation in Hartmannella rhysodes, a small soil amoeba, appear to be an elevated osmotic pressure, Ca2+ and Mg2+, aeration and a decrease in carbon sources. After 36 hr under these conditions, amoebae harvested during active growth encyst. Nutrients essential for growth, other than carbon sources, have no effect on encystation. The factors which bring about encystation are components of the defined medium, in which the minimum essential organic requirements for growth are known.