Excystment of axenically prepared cysts of Hartmanella culbertsoni

Axenically prepared cysts of Hartmannella culbertsoni readily excysted in the presence of heat stable factors prepared from Escherichia coli, Klebsiella aerogenes, Staphylococcus aureus, Sarcina lutea, Bacillus subtilis, Bacillus megaterium and several fungi. Peptone, proteose peptone, tryptone or amino acids also promoted excystment. Crowding of the cysts and dilution of bacterial extracts adversely affected the excystment. Continual presence of the factors in the medium was essential for excystment.