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| Titel |
Arctic gypsum endoliths: a biogeochemical characterization of a viable and active microbial community |
| VerfasserIn |
L. A. Ziolkowski, N. C. S. Mykytczuk, C. R. Omelon, H. Johnson, L. G. Whyte, G. F. Slater |
| 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 ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-27), S.7661-7675 |
| Datensatznummer |
250085441
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| Publikation (Nr.) |
 copernicus.org/bg-10-7661-2013.pdf |
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| Zusammenfassung |
| Extreme environmental conditions such as those found in the polar regions on
Earth are thought to test the limits of life. Microorganisms living in these
environments often seek protection from environmental stresses such as high
UV exposure, desiccation and rapid temperature fluctuations, with one
protective habitat found within rocks. Such endolithic microbial communities,
which often consist of bacteria, fungi, algae and lichens, are small-scale
ecosystems comprised of both producers and consumers. However, the harsh
environmental conditions experienced by polar endolithic communities are
thought to limit microbial diversity and therefore the rate at which they
cycle carbon. In this study, we characterized the microbial community
diversity, turnover rate and microbe–mineral interactions of a gypsum-based
endolithic community in the polar desert of the Canadian high Arctic.
16S/18S/23S rRNA pyrotag sequencing demonstrated the presence of a diverse
community of phototrophic and heterotrophic bacteria, archaea, algae and
fungi. Stable carbon isotope analysis of the viable microbial membranes, as
phospholipid fatty acids and glycolipid fatty acids, confirmed the diversity
observed by molecular techniques and indicated that present-day atmospheric
carbon is assimilated into the microbial community biomass. Uptake of
radiocarbon from atmospheric nuclear weapons testing during the 1960s into
microbial lipids was used as a pulse label to determine that the microbial
community turns over carbon on the order of 10 yr, equivalent to
4.4 g C m−2 yr−1 gross primary productivity. Scanning electron
microscopy (SEM) micrographs indicated that mechanical weathering of gypsum
by freeze–thaw cycles leads to increased porosity, which ultimately
increases the habitability of the rock. In addition, while bacteria were
adhered to these mineral surfaces, chemical analysis by micro-X-ray
fluorescence (μ-XRF) spectroscopy suggests little evidence for
microbial alteration of minerals, which contrasts with other endolithic
habitats. While it is possible that these communities turn over carbon
quickly and leave little evidence of microbe–mineral interaction, an
alternative hypothesis is that the soluble and friable nature of gypsum and
harsh conditions lead to elevated erosion rates, limiting microbial residence
times in this habitat. Regardless, this endolithic community represents a
microbial system that does not rely on a nutrient pool from the host gypsum
cap rock, instead receiving these elements from allochthonous debris to
maintain a more diverse and active community than might have been predicted
in the polar desert of the Canadian high Arctic. |
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