Biogenic Ice Nuclei. Part II: Bacterial Sources

G. Vali University of Wyoming, Laramie 82071

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M. Christensen University of Wyoming, Laramie 82071

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R. W. Fresh University of Wyoming, Laramie 82071

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E. L. Galyan University of Wyoming, Laramie 82071

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L. R. Maki University of Wyoming, Laramie 82071

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R. C. Schnell University of Wyoming, Laramie 82071

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Abstract

Transient appearance of ice nuclei active at temperatures of −2 to −5°C has been noted to accompany the natural decay of plant leaf materials. It was shown that the development of these nuclei results from the presence of a bacterium which was identified as Pseudomonas syringae. These bacteria produce highly active nuclei in a variety of growth media. Evidence points to the fact that the bacterial cells themselves are the nuclei, but that nucleating capacity is a rare and changeable property of the cells. The findings raise the possibility that bacteria may play a role in atmospheric precipitation processes.

Abstract

Transient appearance of ice nuclei active at temperatures of −2 to −5°C has been noted to accompany the natural decay of plant leaf materials. It was shown that the development of these nuclei results from the presence of a bacterium which was identified as Pseudomonas syringae. These bacteria produce highly active nuclei in a variety of growth media. Evidence points to the fact that the bacterial cells themselves are the nuclei, but that nucleating capacity is a rare and changeable property of the cells. The findings raise the possibility that bacteria may play a role in atmospheric precipitation processes.

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