CELL DEATH IN TETRAHYMENA THERMOPHILA: NEW OBSERVATIONS ON CULTURE CONDITIONS

Authors

  • Søren T. Christensen,

    Corresponding author
    1. Institute of Medical Biology, Department of Anatomy and Cell Biology, University of Southern Denmark, Odense, Denmark
    2. Department of Medical Biochemistry and Genetics, The Panum Institute, University of Copenhagen, Denmark
      August Krogh Institute, Biochemistry Department, Copenhagen University, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark. E-mail: stchristensen@aki.ku.dk or tvorup@biobase.dk.
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  • Heidi Sørensen,

    1. Institute of Medical Biology, Department of Anatomy and Cell Biology, University of Southern Denmark, Odense, Denmark
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  • Natascha H. Beyer,

    1. Institute of Medical Biology, Department of Anatomy and Cell Biology, University of Southern Denmark, Odense, Denmark
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  • Karsten Kristiansen,

    1. Institute of Medical Biology, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
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  • Leif Rasmussen,

    1. Institute of Medical Biology, Department of Anatomy and Cell Biology, University of Southern Denmark, Odense, Denmark
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  • Morten I. Rasmussen

    1. Institute of Medical Biology, Department of Anatomy and Cell Biology, University of Southern Denmark, Odense, Denmark
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August Krogh Institute, Biochemistry Department, Copenhagen University, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark. E-mail: stchristensen@aki.ku.dk or tvorup@biobase.dk.

Abstract

We previously suggested that the cell fate of the protozoan ciliate, Tetrahymena thermophila, effectively relates to a quorum-sensing mechanism where cell-released factors support cell survival and proliferation. The cells have to be present above a critical initial density in a chemically defined nutrient medium in order to release a sufficient level of these factors to allow a new colony to flourish. At a relatively high rate of metabolism and/or macromolecular synthesis and below this critical density, cells began to die abruptly within 30min of inoculation, and this death took the form of an explosive disintegration lasting less than 50 milliseconds. The cells died at any location in the culture, and the frequency of cell death was always lower in well-filled vials than those with medium/air interface. Cell death was inhibited by the addition of Actinomycin D or through modifications of the culture conditions either by reducing the oxygen tension or by decreasing the temperature of the growth medium. In addition, plastic caps in well-filled vials release substances, which promote cell survival. The fate of low-density cultures is related to certain ‘physical’ conditions, in addition to the availability of oxygen within closed culture systems.

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