Studies on the Biochemical Basis of the Minimum Temperatures for Growth of Certain Psychrophilic and Mesophilic Micro-organisms

Abstract

Growth, respiratory activity and the ability to accumulate D-glucosamine were examined in three psychrophilic and three related mesophilic micro-organisms at temperatures between 0° and 20°. Each of the psychrophils (strains of Arthrobacter, Candida and Corynebacterium erythrogenes) grew well at 0° and also respired exogenous glucose and accumulated glucosamine at this temperature. The minimum temperatures for growth (5-10°) of the mesophilic strains of Arthrobacter and Candida utilis were approximately the same as those at which the organisms ceased to respire glucose and accumulate glucosamine. But the mesophil Corynebacterium xerosis respired exogenous glucose and accumulated glucosamine at temperatures as low as 10°, which is well below the minimum temperature for growth of this bacterium in freshly inoculated culture (20°). Cultures of C. xerosis transferred from 30° to 15° in the mid-exponential phase of growth were capable of a limited amount of growth at the lower temperature, corresponding approximately to a doubling in the size of the population; late-exponential phase cultures when transferred to 15° did not have this ability. Although cultures of C. xerosis transferred from 30° to 10° did not grow, the bacteria were able to respire exogenous glucose and accumulate glucosamine even after 48 hr at the lower temperature. The psychrophilic organisms did not differ from their mesophilic counterparts in their sensitivity to 2,4-dinitrophenol, uranyl ions and nystatin, three metabolic inhibitors which affect respiratory activity and sugar uptake in microorganisms.