Marine bacteria in deep Arctic and Antarctic ice cores: a proxy for evolution in oceans over 300 million generations
نویسنده
چکیده
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 windtransported 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.
منابع مشابه
Interactive comment on “Marine bacteria in deep Arctic and Antarctic ice cores: a proxy for evolution in oceans over 300 million generations” by P. B. Price and R. C. Bay
It is generally accepted that the major sources of microbial cells transported by atmospheric circulation and deposited with snow on glacial surfaces are terrestrial dust, marine surface aerosols and volcanic ashes. The manuscript of Price and Bay is focused on bacteria of marine origin and more specifically on the autotrophic photosynthetic picocyanobacteria Prochlorococcus and Synechococcus, ...
متن کاملInteractive comment on “Marine bacteria in deep Arctic and Antarctic ice cores: a proxy for evolution in oceans over 300 million generations” by P. B. Price and R. C. Bay
It is generally accepted that the major sources of microbial cells transported by atmospheric circulation and deposited with snow on glacial surfaces are terrestrial dust, marine surface aerosols and volcanic ashes. The manuscript of Price and Bay is focused on bacteria of marine origin and more specifically on the autotrophic photosynthetic picocyanobacteria Prochlorococcus and Synechococcus, ...
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