Polymorphic Properties of Tetrahymena patula During Growth in Axenic Culture*

Abstract

SYNOPSIS. The effects of temperature and pH on growth and polymorphism were studied. The dimorphic condition followed a cyclic nature associated with growth in axenic culture. During logarithmic growth the population consisted of 95–100% microstomes. Upon entering stationary phase the microstomes transformed into macrostomes. The percent microstomes which transformed into macrostomes was found to be affected by culture conditions. When grown at 25°C, pH 7.0, 50% of the population during stationary phase was macrostomes, whereas cultures grown at 25°, pH 7.4, showed 26% macrostomes during stationary phase. Hydrogen ion concentrations higher and lower than this value produced increasingly larger percent of macrostomes during stationary phase. At 20°C, pH 7.0, stationary phase, the population consisted of 100% macrostomes. Generally, those conditions which favored growth in axenic culture also favored the microstome during stationary phase.Large populations of microstomes were induced to transform into macrostomes by transferring a logarithmically growing culture from 25° to 20° or 15°C. Silver impregnated cells showed that the transformation from microstome to macrostome involved oral replacement.It was found that macrostomes, when placed in fresh medium, gave rise to two microstomes through cell division. A direct transformation from macrostome to microstome was not observed.