Properties of Cell-Free Ice Nuclei from Ice Nucleation-Active Pseudomonas fluorescens KUIN-1

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The properties of cell-free ice nuclei (CFIN) from ice nucleation-active Pseudomonas fluorescens KUIN-1 were investigated. CFIN were found to be present in the culture supernatant liquid and were separated from P. fluorecens KUIN-1 by centrifugation, filtration (0.22 μm, pore size) and ultrafiltration. Sucrose was a good carbon source for the ice-nucleating activity of CFIN and L-sodium glutamate was a good nitrogen source. In an ice-nucleating medium in 1 l of water, maximum growth was obtained with production of 118 mg of CFIN at 18℃ after 48 h with shaking. The ice-nucleating activity was greatly decreased by treating CFIN at 40℃ for 30 min and was completely lost by heating at 90℃. The ice-nucleating activity of CFIN was inhibited by the addition of protease K, thermolysin or lipase. However, phospholipase A_2 had no effect. THe freezing difference spectra in D_2O-H_2O for CFIN were similar to the freezing difference spectra in D_2O-H_2O for the cells. Consequently, it could be inferred that there were three types of nucleating activity on CFIN. CFIN active at -3.2〜-4.3℃, -4.5 to -6.1℃ or <>-8.1℃ were arbitrarily assigned into three groups-class A, class B or class C.
公益社団法人日本生物工学会の論文
1993-07-25