Riding The Ciliate Cell Cycle—A Thirty‐Five‐Year Prospective^a

Abstract

Studies of the ciliate cell cycle have moved from early examination of its biochemistry with heat-synchronized Tetrahymena through descriptive studies of Paramecium using small synchronous cell samples. These studies described what happens during the cell cycle and provided some initial insights into control, especially the idea that there was a point at which cells became committed to division. This early work was followed by an analytical phase in which the same small sample techniques, combined with gene mutations, were used to tease apart some major features of the regulation of cell growth kinetics, including regulation of macronuclear DNA content and regulation of cell size, the control of timing of initiation of macronuclear DNA synthesis, and the control of commitment to division in Paramecium. The availability of new molecular genetic approaches and new means of manipulating cells en masse made it possible to map out some of the basic features of the molecular biology of cell cycle regulation in ciliates. The challenge before us is to move beyond the 'me-too-ism' of validating the presence of basic molecular regulative machinery underlying the cell cycle in ciliates to a deeper analysis of the role of specific molecules in processes unique to ciliates or to analysis of the role of regulatory molecules in the control of cell process that can be uniquely well studied in ciliates.

Rumen ciliated protozoa decrease generation time and adjust 18S ribosomal DNA copies to adapt to decreased transfer interval, starvation, and monensin

“…Iwamoto et al (2004) suggested that Tetrahymena thermophila (a nonrumen ciliate) senses its cell volume or macronuclear DNA concentration and coordinates this regulation with nutrient supply and transfer. If not coordinated with transfer (and sudden dilution of cell numbers relative to substrate provision), checkpoints in the cell cycle should subsequently arrest cell division (Berger, 2001). Thus, while verifying reasons for changes in 18S rDNA copies among protozoal standards for use as a biomass marker, 18S rDNA also was hypothesized to be an ideal indicator to evaluate shifts in growth rates among rumen ciliates in cultures undergoing different dietary treatments.…”

Two Forms of Membrane‐Bound Sphingosine Kinase in Tetrahymena and Activity Changes During Growth and the Cell Cycle

“…Tetrahymena is widely employed as a model system to study morphogenesis, conjugation, cell division, growth kinetics, membrane biogenesis, and membrane adaptation (Berger et al2001; Nakashima et al 1996; 1997; Turkewitz, Orias, and Kapler 2002; Wang et al 1998; 1999). As an initial step to understand the role of SPHK in Tetrahymena , changes in SPHK activity were first examined during different stages of culture growth.…”

Variability of Autogamy-Maturation Pattern in Genetically Identical Populations of Paramecium tetraurelia

“…Cell size (Wichterman, 1953;Berger, 2001), serotype (Preer Jr, 1986;Bleyman, 1996) and clonal life span (Takagi et al ., 1987a) are examples in Paramecium . The present study of the autogamy-maturation pattern added another example.…”