CELL MULTIPLICATION IN TETRAHYMENA-SETOSA AND TETRAHYMENA-THERMOPHILAIN SYNTHETIC NUTRIENT MEDIUM - EFFECTS OF ETHANOL, CHOLESTEROL AND EXTRACELLULAR MEDIUM

Cell multiplication in cultures of Tetrahymena setosa and Tetrahymena thermophila was followed under various conditions: in single cell or m ass cultures, and in variations of synthetic nutrient media. The exper imental flasks were inoculated at known concentrations with cells whos e extracellular medium had been replaced by an inorganic buffer. T the rmophila cells failed to multiply at low concentrations of cells or am ino acids, but these situations were reversed by the addition of 10 mu g cholesterol per ml. Also T. setosa failed to multiply at low initial cell concentrations, a situation reversed by the addition of a mixtur e of phospholipids. At high initial cell concentrations T. setosa was grown for months in standard, lipid-free synthetic medium supplemented with 0.2% ethanol. All of these results were unexpected because T. th ermophila has been considered a non-lipid-requirer, since it has been grown in lipid-free synthetic medium for decades, and T. setosa has be en reported to have a lipid requirement. Because there is a critical l ow cell concentration for multiplication, it is believed that these ce lls release multiplication promoting factors and that added lipids som ehow mimick their effects. In agreement with this idea cell-free, extr acellular fluid promoted cell multiplication, even across the borderli ne between the two species.