Axenic Paramecium caudatum. I. Mass Culture and Structure*

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Abstract
To establish and grow P. caudatum in mass axenic culture, the culture medium of Soldo, Godoy and van Wagtendonk was modified by substituting phosphatidylethanolamine (PE) for TEM-4T and by a 10-fold increase in folic acid. Population densities of 4000-6000 cells/ml and a generation time of 20-26 h are regularly obtained. Optimal growth is obtained with PE stigmasterol ratios between 40:1 to 400:1. Cells from 1-day-old axenic cultures have many lipid bodies aggregated in clumps (which disappear in 2 to 3 days) and foci of rough endoplasmic reticulum bordered by dictyosomes. The latter suggests a very active metabolism. Crystalline sheets found in both food vacuoles and lysosomes presumably play a role in digestion. Axenically grown cells also have abundant Golgi bodies (dictyosomes) and by late log phase become filled with lysosomes.