Morphological changes during the growth cycle of axenic and monoxenic Tetrahymena pyriformis

Abstract

Morphometric data were collected from Tetrahymena pyriformis (WH-14, syngen I, mating type II) grown in two different media, one axenic and one monoxenic (with Serratia marcescens), at various times during the growth cycle. Stationary phase cells differed morphometrically from exponential phase cells in different ways in the two media. It is proposed that, in the monoxenic medium, division stopped because the food resource was depleted, while in the axenic medium division was blocked before food limitation occurred.Cells in the two culture media showed consistent morphological differences during exponential phase, the axenic cells being larger (length and width), but having smaller (in length) mouths. Significant differences between cells in replicate experiments were frequently observed.