Paramecium tetraurelia: The Renaissance of an Early Unicellular Model

Abstract

INTRODUCTIONParamecium tetraurelia is a widely distributed, free-living unicellular organism that feeds on bacteria and can easily be cultured in the laboratory. Its position within the phylum Ciliophora, remote from the most commonly used models, offers an interesting perspective on the basic cellular and molecular processes of eukaryotic life. Its large size and complex cellular organization facilitate morphogenetic studies of conserved structures, such as cilia and basal bodies, as well as electrophysiological studies of swimming behavior. Like all ciliates, P. tetraurelia contains two distinct types of nuclei, the germline micronucleus (MIC) and the somatic macronucleus (MAC), which differentiate from copies of the zygotic nucleus after fertilization. The sexual cycle can be managed by controlling food uptake, allowing the study of a developmentally regulated differentiation program in synchronous cultures. Spectacular genome rearrangements occur during the development of the somatic macronucleus. Their epigenetic control by RNA-mediated homology-dependent mechanisms, which might underlie long-known cases of non-Mendelian inheritance, provides evolutionary insight into the diversity of small RNA pathways involved in genome regulation. Being endowed with two alternative modes of sexual reproduction (conjugation and autogamy), P. tetraurelia is ideally suited for genetic analyses, and the recent sequencing of its macronuclear genome revealed one of the largest numbers of genes in any eukaryote. Together with the development of new molecular techniques, including complementation cloning and an easily implemented technique for reverse genetics based on RNA interference (RNAi), these features make P. tetraurelia a very attractive unicellular model.

Centrin diversity and basal body patterning across evolution: new insights fromParamecium

“…Cells were grown at 27°C in a wheat grass infusion (BHB, L'arbre de vie, Luçay Le Male, France) bacterised with Klebsiella pneumoniae and supplemented with 0.4 µg/ml β-sitosterol (Sonneborn, 1970; Beisson et al, 2010). …”

How Do Microbial Populations and Communities Function as Model Systems?

“…Once used as model systems for non-Mendelian inheritance, the unique complexities of ciliates led to their abandonment as genetic models in the late 1960s (Preer 1997;Morange 2006;Montagnes et al 2012). However, a recent resurgence of interest in these complexities-and whether they might be ancestral to and more complex than later eukaryotic simplificationhas renewed the status of paramecia and other ciliates as important model systems (Beisson et al 2010;Bracht et al 2013). Unusual properties of a given organism can make it a useful model for analyzing taxon-specific functions, and the resulting knowledge of a non-typical process then contributes to a wider body of knowledge about more general biological phenomena.…”

Maintaining Clonal Paramecium tetraurelia Cell Lines of Controlled Age through Daily Reisolation

“…Additional procedures are available for the Mass Culture of Paramecium tetraurelia (Beisson et al 2010a). For additional information on the background, husbandry, and potential uses of Paramecium as model organisms, see Paramecium tetraurelia: The Renaissance of an Early Unicellular Model (Beisson et al 2010b). Additional information may also be found in the ParameciumDB wiki: http:// paramecium.cgm.cnrs-gif.fr/parawiki/Protocols.…”