SOME PHYSIOLOGICAL CHANGES OF AN OBLIGATE PSYCHROPHILE AT SUPERMAXIMUM GROWTH TEMPERATURES

Abstract

Some physiological changes during the growth of a psychrophile, Curtobacterium psychrophilum, at supermaximum growth temperatures were studied. Leakage of intracellular materials and cell lysis at 20° were two to three times greater than those at 9°, which is the optimum growth temperature of this bacterium. Decrease of viability at 20° was ten thousand to hundred thousand times of that at 9°. Thermogram at 20° showed one-directioned decrease. Oxygen-uptake was maximum at 15° and completely lost at 40°. Total amount of ATP began to decrease from 3hr later at 20°, while the bacterium grew more rapidly than at 9°. Incorporation of ³H-methionine stopped simultaneously with cessation of growth, and incorporation of ¹⁴C-uracil and ³H-thymidine ceased. On the basis of these facts, this bacterium is considered to be heat labile in multiple points, though protein synthesis seems to be primarily inhibited at 20°.