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| Titel |
Where microorganisms meet rocks in the Earth's Critical Zone |
| VerfasserIn |
D. M. Akob, K. Küsel |
| 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 ; 8, no. 12 ; Nr. 8, no. 12 (2011-12-02), S.3531-3543 |
| Datensatznummer |
250006238
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| Publikation (Nr.) |
 copernicus.org/bg-8-3531-2011.pdf |
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| Zusammenfassung |
| The Critical Zone (CZ) is the Earth's outer shell where all the fundamental
physical, chemical, and biological processes critical for sustaining life
occur and interact. As microbes in the CZ drive many of these biogeochemical
cycles, understanding their impact on life-sustaining processes starts with
an understanding of their biodiversity. In this review, we summarize the
factors controlling where terrestrial CZ microbes (prokaryotes and
micro-eukaryotes) live and what is known about their diversity and function.
Microbes are found throughout the CZ, down to 5 km below the surface, but
their functional roles change with depth due to habitat complexity, e.g. variability
in pore spaces, water, oxygen, and nutrients. Abundances of prokaryotes and
micro-eukaryotes decrease from 1010 or 107 cells g soil−1 or rock−1,
or ml water−1 by up to eight orders of magnitude with depth. Although
symbiotic mycorrhizal fungi and free-living decomposers have been studied
extensively in soil habitats, where they occur up to 103 cells g soil−1,
little is known regarding their identity or impact on
weathering in the deep subsurface. The relatively low abundance of
micro-eukaryotes in the deep subsurface suggests that they are limited in
space, nutrients, are unable to cope with oxygen limitations, or some
combination thereof. Since deep regions of the CZ have limited access to
recent photosynthesis-derived carbon, microbes there depend on deposited
organic material or a chemolithoautotrophic metabolism that allows for a
complete food chain, independent from the surface, although limited energy
flux means cell growth may take tens to thousands of years. Microbes are
found in all regions of the CZ and can mediate important biogeochemical
processes, but more work is needed to understand how microbial populations
influence the links between different regions of the CZ and weathering
processes. With the recent development of "omics" technologies, microbial
ecologists have new methods that can be used to link the composition and
function of in situ microbial communities. In particular, these methods can be used
to search for new metabolic pathways that are relevant to biogeochemical
nutrient cycling and determine how the activity of microorganisms can affect
transport of carbon, particulates, and reactive gases between and within CZ
regions. |
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