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| Titel |
Nitrification rates in Arctic soils are associated with functionally distinct populations of ammonia-oxidizing archaea |
| VerfasserIn |
Ricardo J. E. Alves, Wolfgang Wanek, Anna Zappe, Andreas Richter, Mette M. Svenning, Christa Schleper, Tim Urich |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097184
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| Publikation (Nr.) |
 EGU/EGU2014-12734.pdf |
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| Zusammenfassung |
| The functioning of Arctic soil ecosystems is crucially important for global climate, although
basic knowledge regarding their biogeochemical processes is lacking. Nitrogen (N) is the
major limiting nutrient in these environments, and therefore it is particularly important to
gain a better understanding of the microbial populations catalyzing transformations that
influence N bioavailability. However, microbial communities driving this process remain
largely uncharacterized in Arctic soils, namely those catalyzing the rate-limiting step of
ammonia (NH3) oxidation.
Eleven Arctic soils from Svalbard were analyzed through a polyphasic approach,
including determination of gross nitrification rates through a 15N pool dilution method,
qualitative and quantitative analyses of ammonia-oxidizing archaea (AOA) and bacteria
(AOB) populations based on the functional marker gene amoA (encoding the ammonia
monooxygenase subunit A), and enrichment of AOA in laboratory cultures. AOA were the
only NH3 oxidizers detected in five out of 11 soils, and outnumbered AOB by 1 to 3 orders
of magnitude in most others. AOA showed a great overall phylogenetic diversity
that was differentially distributed across soil ecosystems, and exhibited an uneven
population composition that reflected the dominance of a single AOA phylotype in each
population. Moreover, AOA populations showed a multifactorial association with the soil
properties, which reflected an overall distribution associated with tundra type and with
several physico-chemical parameters combined, namely pH and soil moisture and N
contents (i.e., NO3- and dissolved organic N). Remarkably, the different gross in situ
and potential nitrification rates between soils were associated with distinct AOA
phylogenetic clades, suggesting differences in their nitrifying potential, both under the
native NH3 conditions and as a response to higher NH3 availability. This was further
supported by the selective enrichment of two AOA clades that exhibited different NH3
oxidation rates. In addition, the enrichment cultures provided the first direct evidence
for NH3 oxidation by an AOA from an uncharacterized Thaumarchaeota–AOA
lineage.
Our results indicate that AOA are functionally heterogeneous, and that the selection of
distinct AOA populations by the environment can be determinant for nitrification activity and
N availability in soils. Furthermore, our observations emphasize the fact that, disturbances in
populations of specific microbial functional groups, such as nitrifiers, constitute potential
response mechanisms to environmental changes. These findings are not only relevant for
Arctic environments, but have implications for the role of AOA in nitrification in all soils. |
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