Starvation and Encystment of a Soil Amoeba Hartmannella castellanii*

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Abstract
SYNOPSIS. The behavior of the amoeba H. castellanii was investigated in various carbon and nitrogen deficient media with a view to developing a satisfactory replacement medium for the study of encystment and excystment. Media which had been devised for other soil amoebae did not cause H. castellanii to encyst. In these media there was an efflux of material from the cells which was independent of osmolarity but which was minimized by the addition of magnesium. Maximal encystment occurred in a medium containing magnesium chloride alone.The cysts produced in the magnesium chloride replacement medium are viable and readily excyst when resuspended in the growth medium. The cysts contain cellulose, which is not present in the vegetative amoebae, and differ from the amoebae in their greater resistance to induced lysis and mechanical injury.