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Bacterial community structure and carbon turnover in permafrost-affected soils of the Lena Delta, northeastern Siberia

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Abstract:

Arctic permafrost environments store large amounts of organic carbon. As a result of global warming, intensified permafrost degradation and release of significant quantities of the currently conserved organic matter is predicted for high latitudes. To improve our understanding of the present and future carbon dynamics in climate sensitive permafrost ecosystems, the present study investigates structure and carbon turnover of the bacterial community in a permafrost-affected soil of the Lena Delta (72°22′N, 126°28′E) in northeastern Siberia. 16S rRNA gene clone libraries revealed the presence of all major soil bacterial groups and of the canditate divisions OD1 and OP11. A shift within the bacterial community was observed along the soil profile indicated by the absence of Alphaproteobacteria and Betaproteobacteria and a simultaneous increase in abundance and diversity of fermenting bacteria like Firmicutes and Actinobacteria near the permafrost table. BIOLOG EcoPlates were used to describe the spectrum of utilized carbon sources of the bacterial community in different horizons under in situ temperature conditions in the presence and absence of oxygen. The results revealed distinct qualitative differences in the substrates used and the turnover rates under oxic and anoxic conditions. It can be concluded that constantly negative redox potentials as characteristic for the near permafrost table horizons of the investigated soil did effectively shape the structure of the indigenous bacterial community limiting its phylum-level diversity and carbon turnover capacity.

Le pergélisol situé dans les zones arctiques constitue une vaste réserve de carbone organique. Le réchauffement climatique accroît la dégradation du pergélisol, ayant pour conséquence une libération massive de matière organique prévue dans les régions de hautes latitudes. De manière à améliorer notre compréhension de la dynamique présente et future du carbone dans les écosystèmes climatiques sensibles, telles que le pergélisol, cette étude examine la structure et le turnover du carbone de la communauté bactérienne contenue dans le sol sous influence directe du pergélisol, dans le delta de la Lena (72°22′N, 126°28′E) au nord de la Sibérie. Le clonage du gène 16S rRNA a révélé la présence de la totalité des groupes importants de bactéries du sol, ainsi que des divisions présumées OD1 et OP11. Un changement au sein de la communauté bactérienne a été observé le long du profil de sol, indiqué par l’absence des Alphaproteobacteria et des Betaproteobacteria et l’augmentation simultanée de l’abondance et de la diversité des bactéries fermentatives, comme par exemple les Firmicutes et les Actinobacteria, à proximité du pergélisol. Des plaques BIOLOG Eco ont été utilisées sous conditions de température contrôlées et en présence ou absence d’oxygène, afin de décrire le spectre des sources de carbone utilisées par la communauté bactérienne dans les différents horizons du sol. Les résultats ont révélé des différences qualitatives distinctes concernant les substrats utilisés, ainsi que le turnover du carbone sous conditions oxiques et anoxiques. En conclusion, les potentiels d’oxydo-réduction exclusivement négatifs, caractérisant l’horizon du sol proche du pergélisol, façonnent efficacement la structure de la communauté bactérienne indigène, limitant sa diversité au niveau du phylum, ainsi que sa capacité à utiliser le carbone organique contenu dans le sol.

Document Type: Research Article

Publication date: January 1, 2009

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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