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  Macromolecular fungal ice nuclei in Fusarium: effects of physical and chemical processing

Kunert, A., Pöhlker, M. L., Tang, K., Krevert, C. S., Wieder, C., Speth, K. R., et al. (2019). Macromolecular fungal ice nuclei in Fusarium: effects of physical and chemical processing. Biogeosciences, 16(23), 4647-4659. doi:10.5194/bg-16-4647-2019.

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Kunert, Anna1, Author              
Pöhlker, Mira L.1, Author              
Tang, Kai1, Author              
Krevert, Carola S.1, Author              
Wieder, Carsten1, Author              
Speth, Kai R.1, Author              
Hanson, Linda E.2, Author
Morris, Cindy E.2, Author
Schmale III, David G.2, Author
Pöschl, Ulrich1, Author              
Fröhlich-Nowoisky, Janine1, Author              
1Multiphase Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826290              
2external, ou_persistent22              


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 Abstract: Some biological particles and macromolecules are particularly efficient ice nuclei (IN), triggering ice formation at temperatures close to 0∘C. The impact of biological particles on cloud glaciation and the formation of precipitation is still poorly understood and constitutes a large gap in the scientific understanding of the interactions and coevolution of life and climate. Ice nucleation activity in fungi was first discovered in the cosmopolitan genus Fusarium, which is widespread in soil and plants, has been found in atmospheric aerosol and cloud water samples, and can be regarded as the best studied ice-nucleation-active (IN-active) fungus. The frequency and distribution of ice nucleation activity within Fusarium, however, remains elusive. Here, we tested more than 100 strains from 65 different Fusarium species for ice nucleation activity. In total, ∼ 11% of all tested species included IN-active strains, and ∼ 16% of all tested strains showed ice nucleation activity above -12 ∘C. Besides Fusarium species with known ice nucleation activity, F. armeniacum, F. begoniae, F. concentricum, and F. langsethiae were newly identified as IN-active. The cumulative number of IN per gram of mycelium for all tested Fusarium species was comparable to other biological IN like Sarocladium implicatum, Mortierella alpina, and Snomax (R). Filtration experiments indicate that cell-free ice-nucleating macromolecules (INMs) from Fusarium are smaller than 100 kDa and that molecular aggregates can be formed in solution. Long-term storage and freeze-thaw cycle experiments revealed that the fungal IN in aqueous solution remain active over several months and in the course of repeated freezing and thawing. Exposure to ozone and nitrogen dioxide at atmospherically relevant concentration levels also did not affect the ice nucleation activity. Heat treatments at 40 to 98 ∘C, however, strongly reduced the observed IN concentrations, confirming earlier hypotheses that the INM in Fusarium largely consists of a proteinaceous compound. The frequency and the wide distribution of ice nucleation activity within the genus Fusarium, combined with the stability of the IN under atmospherically relevant conditions, suggest a larger implication of fungal IN on Earth's water cycle and climate than previously assumed.


 Dates: 2019
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: ISI: 000502263600001
DOI: 10.5194/bg-16-4647-2019
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Title: Biogeosciences
  Other : Biogeosciences
Source Genre: Journal
Publ. Info: Katlenburg-Lindau, Germany : Copernicus GmbH on behalf of the European Geosciences Union
Pages: - Volume / Issue: 16 (23) Sequence Number: - Start / End Page: 4647 - 4659 Identifier: ISSN: 1726-4170
CoNE: https://pure.mpg.de/cone/journals/resource/111087929276006