Document Detail

In situ microbial metabolism as a cause of gas anomalies in ice.
MedLine Citation:
PMID:  18550836     Owner:  NLM     Status:  MEDLINE    
Isolated spikes of anomalously high concentrations of N(2)O have been reported at depths in Greenland and Antarctic ice cores corresponding to narrow time intervals over the past approximately 10(5) years. Now, using a calibrated spectrofluorimeter to map protein-bound Trp, a proxy for microbes, versus depth in the 3,053-m GISP2 ice core, we find six depths at which localized spikes of high cell concentrations coincide with N(2)O spikes. We show that the excess gases are consistent with accumulation of in situ metabolic wastes during residence times of the excess microbes in the ice. Because of sparseness of N(2)O measurements and our spectrofluorimetry versus depth, the total number of microbially produced N(2)O spikes in GISP2 is probably much larger than six. Spikes of excess methanogens coincident with CH(4) spikes are found at three depths in the bottom 3% of GISP2, most likely because of methanogenic metabolism in the underlying silty ice, followed by turbulent flow of the lowest approximately 90 m of ice. The apparent rates of in situ production of N(2)O and CH(4) spikes by metabolism are observed to be consistent with a single activation energy, U, and maintain proportionality to exp(-U/RT) over the entire temperature range down to -40 degrees C. Fluorescence of nonmicrobial aerosols in GISP2 ice is distinguishable from microbial fluorescence by its different emission spectra. Our spectrofluorimetric scans throughout the GISP2 ice core lead us to conclude that both microbes and nonmicrobial aerosols are deposited in discontinuous bursts, which may provide a tool for studying wind storms in the distant past.
Robert A Rohde; P Buford Price; Ryan C Bay; Nathan E Bramall
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2008-06-12
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  105     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2008 Jun 
Date Detail:
Created Date:  2008-06-25     Completed Date:  2008-08-19     Revised Date:  2010-09-22    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8667-72     Citation Subset:  IM    
Physics Department, University of California, Berkeley, CA 94720, USA.
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MeSH Terms
Bacteria / metabolism*
Ice Cover / microbiology*
Methane / analysis*,  metabolism
Microscopy, Fluorescence
Nitrogen Dioxide / analysis*,  metabolism
Water Microbiology
Reg. No./Substance:
10102-44-0/Nitrogen Dioxide; 74-82-8/Methane

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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