Identification of a New Ice-nucleating Bacterium and Its Ice Nucleation Properties

A new ice-nucleating bacterium, KUEN-3, was isolated from strawberry leaves. The ice-nucleating bacterium was found in the pale yellow colony group. Strain KUEN-3 was identified as Erwinia uredovora from its taxonomical characteristics. When strain KUIN-3 was cultured aerobically in a medium consisting of Simmons-citric acid broth (pH 6.1) for 24hr at 18°C, the ice-nucleating activity of strain KUIN-3 cells was obtained. The ice-nucleating temperature, T 50 (°C) was detected at −2.8°C in cell suspensions (1.1 × 10 8 cells/ml) of strain KUIN-3. The ice-nucleating temperature was significantly decreased by treating cell suspensions for 30 min at 40°C and was completely lost by heating them at 90°C. The plot of ice-nucleating temperature versus treatment temperature (°C) is similar to the curve that was obtained for cell suspensions of another ice-nucleating bacteria. The susceptibility of cell ice nuclei to urea or protein-modifying reagents suggests that proteins participate in the ice-nucleating event.