Developmental studies on the true slime mold Echinostelium minutum

Abstract

Six cultures of Echinostelium minutum were isolated from dead grass. Single spores and myxamoebae of these isolates produced protoplasmodia and sporangia; hence there was no indication of the presence of a mating-type factor. One isolate, D-3, was established in monoxenic culture with Aerobacter aerogenes and used for subsequent studies. Myxamoebae grown in a dilute glucose – peptone – yeast extract broth had a minimum generation time of 13 h. Conversion of myxamoebae into swarm cells occurred in a liquid environment at a rate independent of the concentration of myxamoebae between 1 × 105–1 × 106 cells/ml. Protoplasmodia, which multiplied by binary fission, had a minimum generation time of 12 h on Ionagar No. 2. Maximum conversion of protoplasmodia into fruiting bodies was produced by subculture to Ionagar No. 2, with approximately 100% conversion being obtained within 48 h. Nearly 100% of the spores were viable if the sporangia matured in the absence of bacterial growth.