Nucleolar and biochemical changes during unbalanced growth of tetrahymena pyriformis

Ivan L. Cameron, E. Ernest Guile

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35 Scopus citations


Numerous nucleoli can be observed in the macronucleus of the logarithmically growing ciliated protozoan Tetrahymena pyriformis; at late log phase the nucleoli aggregate and fuse. In stationary phase this fusion process continues, leaving a very few large vacuolated nuclear fusion bodies in the nucleus. When these stationary phase cclls are placed into frcsh enriched proteose peptone mcdium, the large fusion bodies begin to disaggregate during the 2.5-hour lag phase before cell division is initiated. By 3 to 6 hours after inoculation the appearance of the nucleoli in many cells returns to what it was in logarithmic cells. In view of the possible role of nucleoli in ribosome synthesis, attempts were made to correlate the morphological changes to changes in RNA and protein metabolism. The beginning of an increased RNA synthesis was concomitant with the beginning of disaggregation of the large fusion bodies into nucleoli, which was noticed in some cells by 1 hour after the return to fresh enriched proteose peptone medium. Increased protein synthesis then followed the increased RNA synthesis by 1 hour. Thc supply of RNA precursors (essential pyrimidines) were removed from cultures which were grown on a chemically, defined synthetic medium, in order to study the rclation between nucleolar fusion and synthesis of RNA and protein. Pyrimidine deprivation drastically curtailed RNA and protein synthesis, but did not cause fusion of nucleoli. When pyrimidines were added back to this culture medium, RNA synthesis was immediately stimulated and again preceded an increascd protcin synthesis by 1 hour. Thesc studies suggest the involvement of unfuscd nuclcoli in RNA and protein synthesis and dcmonstrate the extreme plasticity of nucleoli with respect to changes in their environmcnt

Original languageEnglish (US)
Pages (from-to)845-855
Number of pages11
JournalJournal of Cell Biology
Issue number3
StatePublished - Jan 1 1965
Externally publishedYes

ASJC Scopus subject areas

  • Cell Biology


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