Effects of immobilization on growth, morphology, and DNA content of the ciliated protozoon Tetrahymena thermophila

Morphological and physiological properties of Tetrahymena thermophila immobilized by encapsulation in calcium-alginate hollow spheres were found to be substantially different from those of suspended cells. Immobilized T. thermophila reached lengths of 70-100 m, whereas the average cell of suspension cultures was about 40 m long. Suspended cells appeared typically pear-shaped while immobilized cells developed a proboscis-like anterior end. Contrary to suspended T. thermophila, encapsulated cells were functionally deficient in phagocytosis although developing an oral apparatus. The diameter of the macronucleus of immobilized cells was about two times larger than the macronucleus of suspended cells and contained twice as much DNA, while the DNA content of the micronucleus remained unchanged. High cell density fermentations of suspended cells indicated that the alterations observed in immobilized cells were not due to close physical contacts between the cells.