A method for the immobilization of living Tetrahymena

Cytological analysis of Tetrahymena thermophila

Since their first detection in pond water, large ciliates such as Tetrahymena thermophila, have captivated school children and scientists alike with the elegance of their swimming and the beauty of their cortical organization. Indeed, cytology - simply looking at cells - is an important component of most areas of study in cell biology and is particularly intriguing in the large, complex Tetrahymena cell. Cytological analysis of Tetrahymena is critical for the study of the microtubule cytoskeleton, membrane trafficking, complex nuclear movements and interactions, and the cellular remodeling during conjugation, to name a few topics. We briefly review previously reported cytological techniques for both light and electron microscopy, and point the reader to resources to learn about those protocols. We go on to present new and emerging technologies for the study of these marvelous cells. These include the use of fluorescent-protein tagging to localize cellular components in live cells, as well as for tracking the dynamic behavior of proteins using pulse labeling and fluorescence recovery after photobleaching. For electron microscopy, cellular and antigenic preservation has been improved with the use of cryofixation and freeze-substitution. The technologies described here advance Tetrahymena cell biology to the cutting-edge of cytological analysis.

A quantitative assay for ciliate chemotaxis

A quantitative bioassay for ciliate chemotaxis based on the capillary principle is described using Tetrahymena thermophila as test organism. The attractant-containing assay tube designed for the bioassay attracts up to 4 X 10(4) cells in 2 h which makes electronic cell counting of the chemotactic response feasible. The attractants used are solutions of proteose peptone and yeast extract which also are growth media for this organism.

The conjugation junction of Tetrahymena: Its structure and development

The conjugation junction of Tetrahymena has been examined by thin sections, freeze fracture preparations, and by scanning electron microscopy. The junction is formed where the anterior tips of the pairing cells attach to one another. The structure is essentially a large disk composed of two face-to-face plasma membranes separated by a gap of extracellular space measuring about 50 nm. Rows of intramembrane particles are present at the boundary between the junction and ordinary cell cortex. These particles form a ring around the junction. Subjacent to each membrane is a thick mottled layer of material. Pores form in the junction at sites of membrane fusion. Though wider than long, these structures are actually bridges of cytoplasm that connect the conjugating cells. Pores fall into certain size and shape classes, indicating that membrane fusion is highly controlled in this system. At the level of the cytoplasmic bridge the submembrane material is compact and electron-dense. Changes in the structure of the epiplasmic layer have been monitored as the normal cortex is modified during tip transformation and through formation of the mature conjugation junction. Evidence is provided that the submembrane layer plays a significant role in the regulation of pore formation. This cytoskeletal structure may also limit the extent of membrane fusion, thus controlling the size of the cytoplasmic channels.