OBSERVATIONS ON THE PHYSIOLOGY OF PSYCHROPHILISM IN A YEAST

Abstract

In a psychrophilic Candida species, survival, respiration of intact cells, activity of alcohol dehydrogenase, and entry of glucosamine into the cell were more sensitive to temperatures above 10 °C than in a mesophilic species, Candida lipolytica. However, growth was more sensitive to temperature than any of these other properties. Respiration of the psychrophile was more rapid than that of the mesophile at all temperatures up to 30°, the difference being most striking at 0°–10 °C. It is suggested that the upper temperature limit for growth of the psychrophile is set by the reversible inactivation of some vital reaction not yet identified.Uptake of glucosamine in the psychrophile was rapid and the rate only slightly influenced by temperature between 0° and 30°. In contrast there was scarcely any uptake by the mesophile at 0° and 10°, and the rate at 20° was much lower than that at 30°. It is suggested that the lower temperature limit of growth for the mesophile is set by the temperature dependence of the mechanisms for transporting substrates into the cell, and that an increased permeability at low temperatures may be an important factor in permitting some organisms to thrive in the cold.