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Home Reviews Paramecium: Genetics and Epigenetics
Paramecium: Genetics and Epigenetics Print E-mail
Geoffrey H. Beale and John R. Preer, Jr. CRC Press, Boca Raton, Fla., 2008, 216 p., $104.95 (hardcover).

Paramecia are fascinating unicellular, eukaryotic microorganisms, which play an important role in aquatic ecosystems.  More specifically, they are a key link in detritus-based food webs consuming organic debris and microorganisms. When examined under the microscope, various morphological structures can be distinguished, including a buccal cavity and a cytopharynx (used for food intake), two contractile vacuoles (important for expelling water from the cell as a means of balancing its salt concentration), a macronucleus (for day-to-day activities of growth and reproduction), and a micronucleus (which remains relatively dormant until the cell undergoes some type of sexual process). The presence of cilia (important for locomotion) is used for classification: Paramecia belong to the kingdom Protista, subkingdom Protozoa, phylum Ciliophora and class Ciliatea (short: ciliates).

Beale and Preer wrote a fascinating book. They not only provide the reader with a significant amount of background information about these unique microorganisms but also, as the title of their book indicates, discussed in depth the genetics and epigenetics of paramecia. It needs to be mentioned that Paramecium (in addition to Drosophila, peas, maize, and Neurospora) was a model organism in the study of eukaryotic genetics, and it is now a fascinating study object in epigenetics research. The reason for choosing paramecia is obvious, as the authors point out in the Foreword of their book: "It combines the advantages of a free-living, unicellular organism that can be grown rapidly in simple media with those of having a large cell size with an exquisitely complex structure and behavior."

The authors prepared a total of 12 chapters. Each of these chapters is linked in a way that the reader can steadily increase his knowledge. Chapter 1 introduces the reader to the world of paramecia research past and present. It is essentially a historical journey that covers the basic information of early paramecia research up to new epigenetics studies. The second chapter describes the different mating types in Paramecium, including the known cross-reactions among the mating types. The authors mentioned that this chapter was placed at the beginning of their book because the concept of mating types must be understood before analyzing the genetic and epigenetic aspects of these microorganisms.

Chapter 3, entitled "General Description of the Protista and of Paramecium," includes a thorough discussion of their morphology, reproduction, and the life cycle. The following two chapters are about the methods used for studying the genetic processes in organisms of the Paramecium aurelia species group (chapter 4) and about the determination of the inheritance of mating types (chapter 5).

In the sixth chapter, Beale and Preer take a closer look at the effects of the presence of endosymbionts (Caedibacter, Pseudocaedibacter, Lyticum, Tectibacter, and Holospora) in Paramecium. They discuss genetic determinants in the DNA of the symbionts, as well as in the nuclei and in the mitochondria of the host Paramecium. Chapter 7 is about the role of immobilization antigens (i-antigens) of Paramecium, which are certain surface proteins useful for the study of antigenic variation. In the following two chapters, the activities of the micro- and macronuclei of Paramecium are discussed (chapter 8) and of the ribosomal RNA as well as the genes that produce it (rDNA) (chapter 9).

Chapter 10 deals with cortical morphogenesis and inheritance. More specifically, Beale and Preer discuss the surface (cortex) structure of Paramecium, cortical mutants, and trichocysts (sac-like organelles that lie beneath the cell surface). Chapter 11 is about the behavior of Paramecium (e.g., normal swimming behavior, the avoiding reaction, the speed-up response after touch, and the effects of gravity, light, temperature, etc.). The final chapter (Chapter 12) is called "Epigenetics." The authors point out that this term was originally used to describe the genetics of development, and more recently, the study of inheritance that is not dependent on the base sequence of DNA. Beale and Preer define epigenesis as "any inheritance whose pattern of transmission is non- Mendelian."

Beale and Preer prepared a rich text for scientists interested in paramecia and in (eukaryotic) genetics and epigenetics. The book can also be used as a kind of a methods manual. It is fully referenced, well illustrated, and has a useful index. I believe this book is worth the purchase.

Christian T. K.-H. Stadtländer
University of St. Thomas
Minneapolis-St. Paul, Minn.