Identification of a novel ice-nucleating bacterium of Antarctic origin andits ice nucleation properties

A novel ice-nucleating bacterium (INB) was isolated from Ross Island, Antar ctica. INBs could be isolated more frequently than was generally thought. I NB strain IN-74 was found in the white colony group. Strain IN-74 was ident ified from its taxonomic characteristics as a novel INB, Pseudomonas antarc tica IN-74. When strain IN-74 was cultured aerobically in a medium consisti ng of the ice-nucleating broth (pH 7.0) for 6 days at 4 degrees C, the ice- nucleating activity of strain IN-74 cells was obtained. Strain IN-74 cells produced ice nuclei only at extremely low growth temperatures. The nuclei a ppeared to be less thermolabile than those of INB Pseudomonas fluorescens K UIN-1. The freezing difference spectra in D2O and H2O at ice-nucleating tem perature for strain IN-74 cells and conventional INBs (Pseudomonas fluoresc ens KUIN-1, Pseudomonas viridiflava KUIN-2, and Pseudomonas syringae C-9) e xhibited different curves. (C) 1999 Academic Press.