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| Titel |
Fluorescent pseudomonads isolated from Hebridean cloud and rain water produce biosurfactants but do not cause ice nucleation |
| VerfasserIn |
H. E. Ahern, K. A. Walsh, T. C. J. Hill, B. F. Moffett |
| 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 ; 4, no. 1 ; Nr. 4, no. 1 (2007-02-12), S.115-124 |
| Datensatznummer |
250001503
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| Publikation (Nr.) |
 copernicus.org/bg-4-115-2007.pdf |
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| Zusammenfassung |
| Microorganisms were discovered in clouds over 100 years ago but information
on bacterial community structure and function is limited. Clouds may not
only be a niche within which bacteria could thrive but they might also
influence dynamic processes using ice nucleating and cloud condensing
abilities. Cloud and rain samples were collected from two mountains in the
Outer Hebrides, NW Scotland, UK. Community composition was determined using
a combination of amplified 16S ribosomal DNA restriction analysis and
sequencing. 256 clones yielded 100 operational taxonomic units (OTUs) of
which half were related to bacteria from terrestrial psychrophilic
environments. Cloud samples were dominated by a mixture of fluorescent
Pseudomonas spp., some of which have been reported to be ice nucleators. It was
therefore possible that these bacteria were using the ice nucleation (IN)
gene to trigger the Bergeron-Findeisen process of raindrop formation as a
mechanism for dispersal. In this study the IN gene was not detected in any
of the isolates using both polymerase chain reaction (PCR) and differential
scanning calorimetry (DSC). Instead 55% of the total isolates from both
cloud and rain samples displayed significant biosurfactant activity when
analyzed using the drop-collapse technique. All isolates were characterised
as fluorescent pseudomonads. Surfactants have been found to be very
important in lowering atmospheric critical supersaturations required for the
activation of aerosols into cloud condensation nuclei (CCN). It is also
known that surfactants influence cloud droplet size and increase cloud
lifetime and albedo. Some bacteria are known to act as CCN and so it is
conceivable that these fluorescent pseudomonads are using surfactants to
facilitate their activation from aerosols into CCN. This would allow water
scavenging,~countering desiccation, and assist in their widespread
dispersal. |
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