Junichi Tanishita

Identification of an ice-nucleating bacterium and its ice nucleation properties

Abstract An ice-nucleating bacterium, KUIN-2, was isolated from carrot leaves. The ice-nucleating bacterium was found in the white colony group. KUIN-2 was identified as Pseudomonas viridiflava from its taxonomic characteristics. When KUIN-2 was cultured aerobically in a medium consisting of Trypticase soy broth (pH 6.0) for 24 h at 18°C, the ice-nucleating activity of KUIN-2 cells was obtained. Ice nucleation was detected at −2.8°C in cell suspensions (1.4 × 10 8 cells/ml) of KUIN-2. The nucleation frequency of KUIN-2 was greatly inhibited by the addition of urea or N -ethylmaleimide.

Ice-nucleating activity of Pseudomonas fluorescens

Abstract Pseudomonas fluorescens KUIN-1 can cause the freezing of water at relatively warm termperatures (−2.9 to −30°C). Glucose, glycerol, and citric acid were good substrates yielding cells with high ice-nucleating activity. Ammonium salts were good nitrogen sourcfes yielding cells with high ice-nucleating activity. The ice-nucleating activity of KUIN-1 was not affected by pH between pH 5.5 to pH 8.0. The ice-nucleating activity of cells was greatly influenced by heat treatment.