SOME FACTORS NECESSARY TO PRODUCE DIVISION CONDITIONS IN TETRAHYMENA PYRIFORMIS

Abstract

The present article was designed to investigate the metabolic processes indispensable for cell division in Tetrahymena pyriformis W and to clarify some characteristics of these activities, in an attempt to demonstrate a generalized mechanism of cell division. Temperature-induced synchronized divisions are completely suppressed by addition of 0.03,M_NaF, while they are scarecely influenced by addition of 0.005 M_NaF at the end of heat-treatment. An interesting inhibition is observed when cultures are exposed to 0.01 M NaF at the end of heat-treatment the 1st synchronous division is exhibited as normal, while the 2nd is completely suppressed. The biological meaning of the different concentrations of the agent resulting in complete inhibition of the 1st and 2nd synchronous divisions may be that some activities occurring within one generation are related not only to the next division but also to further divisions, according to the results derived from the studies on effects of short or long exposure to 0.03 M or 0.01 M NaF on cells of various ages. ATPase activities were measured in synchronized cells exposed to 0.005 M, 0.01 M. and 0.03 M NaF. Regardless of when the divisions occur, peaks of ATPase activity regularly appear about 30-40 minutes prior to synchronous division maxima; on the contrary, pronounced culmination of the enzymatic activity does not appear at all when divisions are completely suppressed. ATPase activity indispensable for the succeeding division is estimated as only small fraction (about 23%) of the total activity observed 30-40 minutes prior to synchronous division maximum. Log phase cells grown in proteose-peptone or synthetic media are able to divide one or more times when they are transferred to synthetic media deprived of various groups of nutrients except amino acids. Log phase cells probably have stores of nutrients or their derivatives to a greater or lesser extent. This indicates that the total amount of a cellular component may not always be critical to the next division. Most log phase cells (70% of the total) are unable to divide when transferred to amino acids-free or methionine-free media. This indicates that only those cells which have passed through more than 70% (157 minutes) of one generation (210 minutes) are able to divide in the amino acids-free medium, the remainder must take up amino acids from the sources and synthesize a specific protein for cell division. The specific protein seems to be related to cytokinesis; and the critical point in its synthesis may take place approximately at the time when the oxidative phosphorylation system shows its greatest activity, since the pool of free amino acids in the cell at 147 minutes is sufficient to permit protein synthesis to continue until this time. The relationship between oxidative phosphorylation and specific protein synthesis indispensable for division is discussed. Production of division conditions may be induced by cooperation of these 2 metabolic activities.