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| Titel |
High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments |
| VerfasserIn |
K. Junge, B. D. Swanson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 5, no. 3 ; Nr. 5, no. 3 (2008-05-22), S.865-873 |
| Datensatznummer |
250002527
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| Publikation (Nr.) |
 copernicus.org/bg-5-865-2008.pdf |
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| Zusammenfassung |
| Even though studies of Arctic ice forming particles suggest that a bacterial
or viral source derived from open leads could be important for ice formation
in Arctic clouds (Bigg and Leck, 2001), the ice nucleation potential of most
polar marine psychrophiles or viruses has not been examined under conditions
more closely resembling those in the atmosphere. In this paper, we examined
the ice nucleation activity (INA) of several representative Arctic and
Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus.
High-resolution ice nucleation spectra were obtained for droplets containing
bacterial cells or virus particles using a free-fall freezing tube
technique. The fraction of frozen droplets at a particular droplet
temperature was determined by measuring the depolarized light scattering
intensity from solution droplets in free-fall. Our experiments revealed that
all sea-ice isolates and the virus nucleated ice at temperatures very close
to the homogeneous nucleation temperature for the nucleation medium – which
for artificial seawater was –42.2±0.3°C. Our results suggest
that immersion freezing of these marine psychro-active bacteria and viruses
would not be important for heterogeneous ice nucleation processes in polar
clouds or to the formation of sea ice. These results also suggested that
avoidance of ice formation in close proximity to cell surfaces might be one
of the cold-adaptation and survival strategies for sea-ice bacteria. The
fact that INA occurs at such low temperature could constitute one factor
that explains the persistence of metabolic activities at temperatures far
below the freezing point of seawater. |
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