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| Titel |
Marine bacteria in deep Arctic and Antarctic ice cores: a proxy for evolution in oceans over 300 million generations |
| VerfasserIn |
P. B. Price, R. C. Bay |
| 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 ; 9, no. 10 ; Nr. 9, no. 10 (2012-10-05), S.3799-3815 |
| Datensatznummer |
250007321
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| Publikation (Nr.) |
 copernicus.org/bg-9-3799-2012.pdf |
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| Zusammenfassung |
| Using fluorescence spectrometry to map autofluorescence of chlorophyll (Chl)
and tryptophan (Trp) versus depth in polar ice cores in the US National Ice
Core Laboratory, we found that the Chl and Trp concentrations often showed an
annual modulation of up to 25%, with peaks at depths corresponding to
local summers. Using epifluorescence microscopy (EFM) and flow cytometry
(FCM) triggered on red fluorescence at 670 nm to study microbes from
unstained melts of the polar ice, we inferred that picocyanobacteria may have
been responsible for the red fluorescence in the cores. Micron-size bacteria
in all ice melts from Arctic and Antarctic sites showed FCM patterns of
scattering and of red vs. orange fluorescence (interpreted as due to Chl
vs. phycoerythrin (PE)) that bore similarities to patterns of cultures of
unstained picocyanobacteria Prochlorococcus and
Synechococcus. Concentrations in ice from all sites were low, but
measurable at ~ 1 to ~ 103 cells cm−3. Calibrations
showed that FCM patterns of mineral grains and volcanic ash could be
distinguished from microbes with high efficiency by triggering on scattering
instead of by red fluorescence. Average Chl and PE autofluorescence
intensities showed no decrease per cell with time during up to 150 000 yr
of storage in glacial ice. Taking into account the annual modulation of
~ 25% and seasonal changes of ocean temperatures and winds, we
suggest that picocyanobacteria are wind-transported year-round from warmer
ocean waters onto polar ice. Ice cores offer the opportunity to study
evolution of marine microbes over ~ 300 million generations by
analysing their genomes vs. depth in glacial ice over the last 700 000
yr as frozen proxies for changes in their genomes in oceans. |
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