SUMMARY: A psychrophilic species of , freshly inoculated cultures of which grew well in a glucose + salts + vitamins medium at 16° but not at all at 30°, was induced to grow rapidly for a period at 30° by previous incubation at 16°. A study was made of certain aspects of the biochemical composition of the cryptococcus in cultures maintained at 16° as compared with that in cultures transferred from 16° to 30°, in order to obtain information about the biochemical basis of the low maximum growth temperature for this organism. With the cryptococcus transferred from 16° to 30°, there was rapid utilization of intracellular reserves of total amino acids and total oxo acids. Exogenous sources of amino acids were unable to replenish the intracellular amino acid pool in the cryptococcus incubated at 30°. However, addition of α-oxoglutarate, citrate, or -citrate to cultures transferred to 30° after 120 hr. at 16° enabled the cryptococcus to continue to grow at the higher temperature; stimulation of growth at 30° was most marked in cultures supplemented with α-oxoglutarate. Other tricarboxylic acid cycle and related intermediates (pyruvate, acetate, succinate, fumarate, -malate, oxaloacetate) had no growth-promoting effect. Stimulation of growth at 30° in the presence of α-oxoglutarate was obtained only in cultures which had been incubated for 2–4 days at 16°, indicating the existence of other temperature-sensitive metabolic processes in addition to those concerned in α-oxoglutarate synthesis.


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