Effects of Cultural Temperatures on the Ice Nucleation Activities of INA Pseudomonas syringae

The study was conducted to clarify the effects of cultural temperature on the activities of INA (ice nucleation-active) bacteria Pseudomonas syringae.INA bacteria were cuttured at 5 levels of temperature (0, 10, 20, 25 and 30°C) for 1 to 5 days of cultural periods respectively. The soybean leaflets contacted with the suspension of these INA bacteria cultured under above cultural conditions. The ice nucleation activities were evaluated through the freezing temperatures of water droplets suspended with INA bacteria and of soybean leaflets spread with INA bacterial suspension.There were no large differences between the freezing temperatures of water droplets suspended with INA bacteria cultured under the temperature condition of 20°C and below. However, the freezing temperatures of droplets suspended with INA bacteria cultured at 25 and 30°C decreased with the cultural duration.On the other hand, the freezing temperatures of soybean leaflets also dependent on cultural temperature, although they were generally lower than those of water droplets. The ice nucleation activities of the INA bacteria cultured under 25 and 30°C were almost nil.