Regulation of RNA synthesis in Tetrahymena pyriformis: secretion of regulatory factors

1979 ◽  
Vol 35 (1) ◽  
pp. 17-24
Author(s):  
H.A. Andersen ◽  
S.J. Nielsen
Keyword(s):  
Stationary Phase ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Initial Rate ◽  
Tetrahymena Pyriformis ◽  
Dose Effect ◽  
Exponential Growth Phase ◽  
Lag Phase ◽  
Cell Densities ◽  
Phase Population

The rate of ribosomal RNA synthesis varies greatly with the population density in both exponentially and synchronously growing populations of Tetrahymena pyriformis. Shortly after inoculation of the population - at relatively low cell densities - a gene-dose effect dominates the picture, and a doubling in the gene number is immediately followed by a doubling in the rate of RNA synthesis. However, also other mechanisms are controlling the rate of RNA synthesis. Generally one finds high rates of RNA synthesis in the lag phase of newly inoculated cells, decreasing rate of RNA synthesis during most of the exponential growth phase and very low rate of synthesis in stationary phase cells. We now have results which show that the repression of RNA synthesis in densely populated cultures is caused by a dialysable factor, which is secreted by the cells. If cells are inoculated on a medium which contains this factor the high initial rate of RNA synthesis normally observed is prevented, but the cells multiply and grow with normal generation time until normal stationary-phase population densities are reached.

scholarly journals NUCLEOLAR AND BIOCHEMICAL CHANGES DURING UNBALANCED GROWTH OF TETRAHYMENA PYRIFORMIS

1965 ◽  
Vol 26 (3) ◽  
pp. 845-855 ◽  
Author(s):  
Ivan L. Cameron ◽  
E. Ernest Guile
Keyword(s):  
Protein Synthesis ◽  
Stationary Phase ◽  
Rna Synthesis ◽  
Morphological Changes ◽  
Synthetic Medium ◽  
Tetrahymena Pyriformis ◽  
Lag Phase ◽  
Proteose Peptone ◽  
Rna And Protein Synthesis ◽  
Peptone Medium

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 cells are placed into fresh enriched proteose peptone medium, 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. The supply of RNA precursors (essential pyrimidines) were removed from cultures which were grown on a chemically defined synthetic medium, in order to study the relation 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 increased protein synthesis by 1 hour. These studies suggest the involvement of unfused nucleoli in RNA and protein synthesis and demonstrate the extreme plasticity of nucleoli with respect to changes in their environment.

Preferential inhibition of rDNA transcription by 5-bromodeoxyuridine

1977 ◽  
Vol 25 (1) ◽  
pp. 95-102
Author(s):  
A.E. Lykkesfeldt ◽  
H.A. Andersen
Keyword(s):  
Growth Medium ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Tetrahymena Pyriformis ◽  
Degree Of Substitution ◽  
Rdna Transcription ◽  
Total Rna

On a chemically defined growth medium the degree of substitution of thymidine with 5-bromodeoxyuridine (BUdR) in DNA of Tetrahymena pyriformis was controlled by the concentration of tetrahydrofiolic acid, BUdR and thymidine in the medium. A correlation between the degree of BUdR substitution in DNA and the reduction in rate of total RNA synthesis has been established. It was found that the reduction of total RNA synthesis results from inhibition of transcription of all RNA species which have been measured. However, independent of the degree of BUdR substitution in DNA, a preferential inhibition of the synthesis of 25s and 17s ribosomal RNA was found. It is concluded that the various genes may respond differently to BUdR substitution with respect to transcription.

Modeling the Physiological State of the Inoculum and CO2 Atmosphere on the Lag Phase and Growth Rate of Listeria monocytogenes

2008 ◽  
Vol 71 (9) ◽  
pp. 1915-1918 ◽  
Author(s):  
ANTONIO J. DE JESÚS ◽  
RICHARD C. WHITING
Keyword(s):  
Stationary Phase ◽  
Growth Phase ◽  
Growth Rates ◽  
Exponential Growth ◽  
Physiological State ◽  
Brain Heart Infusion ◽  
Exponential Growth Phase ◽  
Lag Phase ◽  
Co2 Concentrations ◽  
Co2 Atmosphere

In previous studies, the growth of L. monocytogenes has been modeled under different CO2 headspace concentrations; however, the inoculum cells were always in the stationary phase. In this study, the growth of L. monocytogenes under different CO2 concentrations as affected by the physiological state of the cells was investigated. Exponential-growth-phase, stationary-phase, dried, and starved cells were prepared and inoculated at 5°C into brain heart infusion broths that had been preequilibrated under atmospheres of 0, 20, 40, 60, or 80% CO2 (the balance was N2). Lag-phase duration times (LDTs) and exponential growth rates were determined by enumerating cells at appropriate time intervals and by fitting the data to a three-phase linear function that has a lag period before the initiation of exponential growth. Longer LDTs were observed as the CO2 concentration increased, with no growth observed at 80% CO2. For example, the LDTs for exponential-phase, stationary-phase, starved, and dried cells were 2.21, 8.27, 9.17, and 9.67 days, respectively, under the 40% CO2 atmosphere. In general, exponential-growth-phase cells had the shortest LDT followed by starved cells and stationary-phase cells. Dried cells had the longest LDT. Exponential growth rates decreased as the CO2 concentrations increased. Once exponential growth was attained, no retained differences among the various initial physiological states of the cells for any of the atmospheres were observed in the exponential growth rates. The exponential growth rates under 0, 20, 40, 60, and 80% CO2 averaged 0.39, 0.37, 0.23, 0.23, and 0.0 log CFU/day, respectively. Dimensionless factors were calculated that describe the inhibitory action of CO2 on the LDTs and exponential growth rates for the various physiological states.

Regulation of ribosomal RNA synthesis in Tetrahymena pyriformis

1978 ◽  
Vol 31 (1) ◽  
pp. 13-23
Author(s):  
J. Keiding ◽  
H.A. Andersen
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Tetrahymena Pyriformis ◽  
Rrna Synthesis ◽  
Constant Rate ◽  
Normal Increase ◽  
S Period ◽  
Dosis Effect

Ribosomal RNA is synthesized at constant rate during most of the cell cycle in heat-shock synchronized populations of Tetrahymena pyriformis. Early in each macronuclear S-period the rate of synthesis increases abruptly, concomitant with replication of the genes coding for ribosomal RNA. The increase is prevented by inhibitors of DNA replication, added prior to the S-period. Similarly, in cultures synchronized by starvation/refeeding, inhibition of DNA replication, at the time when the rDNA is replicated, will prevent the normal increase in rate of RNA synthesis which follows refeeding. We conclude that inhibition of rDNA replication interferes with the synthesis of rRNA, and we suggest that with respect to rRNA synthesis a gene dosis effect is operating in fast-growing Tetrahymena cells.

Inhibition of rRNA synthesis following incorporation of 5-bromodeoxyuridine into DNA of Tetrahymena pyriformis

1975 ◽  
Vol 17 (3) ◽  
pp. 495-502
Author(s):  
A.E. Lykkesfeldt ◽  
H.A. Andersen
Keyword(s):  
Dna Replication ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Nuclear Dna ◽  
Tetrahymena Pyriformis ◽  
Growth Conditions ◽  
Defined Medium ◽  
Rrna Synthesis ◽  
Chemically Defined Medium ◽  
Dividing Cells

Tetrahymena pyriformis was grown on chemically defined medium in the presence of 5-bromodeoxyuridine (BUdR). Under these growth conditions more than 60% of the thymidine sites in DNA were substituted with BUdR. It was found that RNA synthesis was strongly inhibited by the presence of BUdR in DNA. To assure that incorporation of BUdR into DNA was a prerequisite of the effect observed, BUdR was added to synchronously dividing cells. BUdR had no effect on the cells when present outside the period of nuclear DNA replication, whereas RNA synthesis was strongly inhibited as soon as the genes coding for ribosomal RNA had replicated in the presence of BUdR.

On the role of small peptides in the regulation of RNA synthesis in Tetrahymena pyriformis

1980 ◽  
Vol 45 (1) ◽  
pp. 31-39
Author(s):  
H.A. Andersen ◽  
A.E. Lykkesfeldt ◽  
S.J. Nielsen
Keyword(s):  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Tetrahymena Pyriformis ◽  
Defined Medium ◽  
Specific Factor ◽  
Small Peptides ◽  
In Vitro Synthesis

Tetrahymena cells secrete a factor which inhibits RNA synthesis in vivo and in vitro. The factor is a relatively small peptide with a molecular weight between 300 and 1500 Daltons. Other, non-specific peptides in the broth medium or added to a chemically defined medium have a stimulatory effect on RNA synthesis in vivo and such peptides also stimulate the in vitro synthesis of RNA in a r-chromatin preparation. On the basis of these results we conclude that such extracellular small peptides compete with a specific factor which is part of the intracellular regulatory mechanism controlling the rate of RNA synthesis. The consequence of such competition is a high overproduction of ribosomal RNA in cells inoculated on peptide-rich broth media.

scholarly journals Dolichyl phosphate phosphatase from Tetrahymena pyriformis

1981 ◽  
Vol 197 (1) ◽  
pp. 233-238 ◽  
Author(s):  
G S Adrian ◽  
R W Keenan
Keyword(s):  
Growth Phase ◽  
Exponential Growth ◽  
Tetrahymena Pyriformis ◽  
Enzymic Activity ◽  
The Other ◽  
Exponential Growth Phase ◽  
Lag Phase ◽  
Mitochondrial Membranes ◽  
Dolichyl Phosphate ◽  
Regulation Of Synthesis

A soluble dolichyl phosphate phosphatase from Tetrahymena pyriformis was purified about 68-fold. The enzyme appeared to be specific for dolichyl phosphate and existed in two interrelated forms, one of mol.wt. about 500000 and the other of mol.wt. about 63000. The enzyme was strongly inhibited by 5 mM-Mn2+ and was strongly stimulated by Mg2+. Tetrahymena in the exponential growth phase contained more of this enzymic activity than cells in stationary or lag phase. The dolichyl phosphate phosphatase may be loosely bound to mitochondrial membranes. Two roles proposed for this enzyme are (1) that of releasing dolichol from its phosphorylated biosynthetic form for its use in the cell as unesterified dolichol or dolichyl ester and/or (2) that of regulation of synthesis of glycoproteins or some other glycosylated compound.

scholarly journals Changes in the transport of mitochondrial Ca2+ during the culture growth cycle of Tetrahymena pyriformis

1985 ◽  
Vol 77 (1) ◽  
pp. 47-56
Author(s):  
Y.V. Kim ◽  
LYu Kudzina ◽  
V.P. Zinchenko ◽  
Y.V. Evtodienko
Keyword(s):  
Stationary Phase ◽  
Morphological Changes ◽  
Stationary Phases ◽  
Mitochondrial Protein ◽  
Tetrahymena Pyriformis ◽  
Growth Cycle ◽  
Lag Phase ◽  
Rapid Release ◽  
Culture Growth ◽  
Energy Dependent

The properties of the Ca2+ transport system of mitochondria, isolated in various phases of growth of static cultures of Tetrahymena pyriformis, were studied. A large increase in the endogenous energy-dependent Ca2+ content of mitochondria was observed as cultures of T. pyriformis passed through the exponential and stationary phases of growth (approx. 0.25 and 50 nmol Ca2+ per mg mitochondrial protein, respectively). Simultaneously, the mitochondria dramatically lost their ability to withstand large concentrations of Ca2+ and ADP. However, in the latter case they were able to phosphorylate a large amount of ADP if the strong Ca2+ chelator, ethylene glycol bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, was initially present in the incubation medium. Furthermore, all the changes observed in mitochondria from the stationary phase cells were completely reversed when cell proliferation was re-activated after the lag phase, either by reseeding the stationery cells in fresh growth medium or by oxygenation of the old medium. In aerobic conditions even a small addition of Ca2+ was able to induce rapid release of Ca2+ from mitochondria isolated during the stationary phase of growth. It is suggested that the redistribution of Ca2+ between the mitochondria and the cytoplasm at the onset of the lag phase may serve as the main trigger for the subsequent biochemical and morphological changes observed in T. pyriformis.

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