A study of plasmodium formation by the true slime mold, Didymium nigripes

Abstract

A technique is described by which it is believed that plasmodia resulting from the fusion of two amoebae are isolated. The rate of plasmodium formation can also be studied using this method. Washed myxamoebae harvested during the logarithmic phase of growth were incubated in M/200, pH 6.2 phosphate buffer containing 1 × 10 −3 M SrCl 2. Samples were diluted appropriately and plated with bacteria. Forty-four hours later the incubated plates were scored for the presence of small clonal plasmodia, free from myxamoebae. The number of such plasmodial clones was used as an index of plasmodium formation. The optimal concentration of ameobae was found to be 2.5 × 10 5/ml. During the first 4 hours of incubation, few plasmodia formed. They appeared at an exponential rate until the twelfth hour of incubation. Fusing pairs of myxamoebae were isolated by micromanipulation. A number of these grew into normal plasmodia.