A PSYCHROPHILIC CRYPTOCOCCUS

Abstract

A psychrophilic yeast, isolated from decomposing Laminaria found on the beach at Hebron Fjord in Labrador, was shown to be a species of Cryptococcus, closely resembling but not identical with C. mucorugosus and C. terricolus. In a glucose–salts–vitamins medium, the yeast grew most rapidly at 25 °C, although the final cell crop was greatest in cultures incubated at 21 °C. The yeast grew well at 3 °C after a lag period of approximately five days, but no growth was observed in cultures incubated throughout at 30 °C or above. Cultures of the yeast which had been incubated at 30 °C, but not at 37 °C, grew, on being transferred to 16 °C, after a lag period that was proportional to the duration of incubation at 30 °C. The yeast grew well at 30 °C after cultures had been incubated for a period at 16 °C, although growth ceased at this higher temperature after a few days; further growth at 30 °C could be obtained after the cultures had again been incubated at 16 °C. The significance of these results is discussed in relation to the psychrophilic behavior of the yeast.