ALBERT

Description: The Arctic plays a key role in the Earths climate system, because global warming is predicted to be most pronounced at high latitudes, and one third of the global carbon pool is stored in ecosystems of the northern latitudes. The degradation of permafrost and the associated release of climate-relevant trace gases from intensified microbial turnover of organic carbon and from destabilized gas hydrates represent a potential environmental hazard.The microorganisms, which are the drivers of methane production and oxidation in Arctic wetlands, have remained obscure. Their function, population structure and reaction to environmental change is largely unknown, which means that also an important part of the process knowledge on methane fluxes in permafrost ecosystems is far from completely understood. This hampers prediction of the effects of climate warming on arctic methane fluxes. Understanding these microbial populations is therefore highly important for understanding the global climatic effects of a warming Arctic. This talk will examine the activity and diversity of methane-cycling microorganisms in Siberian permafrost ecosystems.

Description: Livingston Island, located at the tip of the Antarctic Peninsula (Fig. 1),is characterised by an oceanic polar climate with temperatures above0°C for 4 months per year and a mean annual precipitation between 400and 500 mm. Under these conditions a soil formation can be observedand lichens, mosses and some higher plants are able to grow in thisenvironment. Since cultivation-independent methods have become animportant tool to investigate environmental microbes, it is possible toanalyze complex microbial networks in the face of diversity, abundance,ecology and their reaction on climate change. Here, we investigated thebacterial community structure of different soil and sediment habitatslocated on Livingston Island by polymerase chain reaction (PCR) usinga specific primer set followed by denaturing gradient gelelectrophoresis (DGGE) to get a first insight in the diversity of bacteriaexisting under these conditions. The aim of these studies is to identifythe main microbial players in nutrient turnover and to get an idea of thefunctioning of microbes within periglacial ecosystems.

Description: Livingston Island, located at the tip of the Antarctic Peninsula, is characterised by an oceanic polar climate with temperatures above 0°C during the austral summer and a mean annual precipitation between 400 and 500 mm. Under these conditions a soil formation can be observed and lichens, mosses and some higher plants are able to grow in this environment. With cultivation-independent methods, it is possible to analyse complex microbial networks in the face of diversity, abundance, ecology and their reaction on climate change. Here, we investigated the bacterial community structure of different habitats located on Livingston Island by polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) to get a first insight in the diversity of bacteria existing under these conditions. The aim of these studies is to identify the main microbial players in nutrient turnover within periglacial ecosystems of Antarctica.One transect and four separate profiles were sampled near the Bulgarian station St. Kliment Ohridski (62°38`S/60°21`W). Two soil profiles were characterised by permafrost. The investigated mineral soils showed mostly gravely sand texture. Moisture content of the soils ranged from 2.6% up to 15.6% and was partly quite variable within the different profiles. The values of total carbon and nitrogen were extremely low with 〈0.10 to 0.46% and 〈0.10%, respectively, except for the upper layers of the profiles T1-1 and T1-4 that were covered by mosses. PLFA concentration decreased with increasing depth, which correlates well with the TC values. DGGE patterns from amplification of DNA showed large varieties in the vertical profiles and between the different sites. Most sequences recovered from Antarctic soil profiles belong to the Bacteriodetes and to the Acidobacteria phylum.DGGE pictures showed a high diversity in most of the samples. The main influence on heterotrophic microbial growth and activity in low-nutrient habitats is probably the availability of organic compounds. Water can also be a limiting factor, but microorganisms seem to be well adapted to these conditions as it can be derived from the DGGE pattern. It is conceivable that the ways of C and N cycling in cold Antarctic habitats are short and that cold-adapted microorganisms might play a major role for the ecosystem development. To compare arctic and antarctic microbial communities phylogenetic investigations will be done using clone libraries for both Bacteria and Archaea.

Description: Microorganisms can be found in very different cold soil environments playing a major role in nutrient cycling in these habitats. We studied the dominant bacterial composition from nine soil profiles located on Livingston Island, Antarctica. Two vegetated sites (moss-covered) and seven mineral soil sites were analysed. Total carbon (TC) and total nitrogen (TN) values were up to 26.50 % and 0.84%, respectively, for vegetated soils decreasing with depth whereas values for mineral soils were 〈0.50% and 〈0.10%, respectively. Soil pH was more acidic for vegetated and neutral to alkaline for mineral soils. Conductivity was low at all sites. Numbers of culturable heterotrophic bacteria were higher at vegetated sites. Nonetheless, significant numbers of culturable heterotrophs (102-105 cells g-1 dry weight) were found even in carbon depleted soils. DGGE fingerprints revealed a highly heterogeneous picture throughout the soil profiles. Subsequent sequencing of DGGE bands revealed in total 183 sequences that were affiliated to Acidobacteria, Actinobacteria, Bacteroidetes/Chlorobi, Chloroflexi, Cyanobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria, and candidate divisions OD1 and TM7. Sequences could be assigned to altogether 87 OTUs, with a dominance of Bacteroidetes and Acidobacteria. PLFA analysis showed a lack in unsaturated fatty acids for most samples. Samples with prevalence of unsaturated over saturated fatty acids were restricted to several surface samples. It can be concluded that the presence of plants had an influence on the bacterial community composition by providing organic nutrients. Nevertheless, also bare maritime Antarctic mineral soils showed a diverse microbial composition with species so far untraced in other habitats.

Description: Livingston Island (South Shetland Islands) is characterised by a maritime polar climate with temperatures above 0°C for 4 months and a mean annual precipitation of 450 mm. Nine vertical profiles were investigated regarding to their geochemical and geophysical properties and their microbial community structures. Two of the sites were covered by mosses and showed initial soil formation and humus accumulation. Total carbon and total nitrogen contents were low except for the upper layers of the moss covered sites. Denaturing gradient gel electrophoresis (DGGE) fingerprints from amplified 16S rRNA gene fragments showed large varieties in the vertical profiles and between the different sites. Most of the sequences obtained from re-amplified DGGE bands belong to the Bacteriodetes and Acidobacteria phyla. We also found sequences affiliated to methanotrophic bacteria (Methylobacter, Methylocapsa, Methylocystis) as well as to microorganisms involved in the nitrogen cycle (Nitrospira, Nitrospina). Furthermore, it was possible to isolate pure cultures, which belong mainly to Arthrobacter and Pseudomonas but also members of Frigoribacterium, Devosia, Leifsonia, Subtercola and Mucilaginibacter could be isolated. Although nutrient content is low a distinct diversity of microorganisms can be found in these extreme habitats dominated by so far unknown species.

Description: In der vorliegenden Arbeit wurde die Biodiversität methanogener Archaeen in arktischen Böden des Lena-Deltas / Sibirien unter Verwendung klassischer mikrobiologischer und molekularbiologischer Methoden untersucht. Dazu wurden die Aktivitätspotentiale der Methan bildenden Mikroorganismen in Abhängigkeit von verschiedenen Substraten und Temperaturen untersucht. Mit Hilfe der Denaturierenden Gradienten Gelelektrophorese (DGGE) und anschließender Sequenzierung einzelner DNA-Banden konnten dabei Unterschiede in der Populationszusammensetzung der methanbildenden Gemeinschaft im Tiefenprofil von Permafrostböden aufgezeigt und erklärt werden. Es ist bekannt, dass die Methanogenese in arktischen Böden von vielen verschiedenen klimatischen und bodenspezifischen Faktoren abhängig ist. Vor allem der Gehalt an organischer Substanz hatte einen großen Einfluss auf die Methanbildung. So förderte die Zugabe von Substrat die Methanbildung meist erheblich. Dabei war mit H2/CO2 der höchste Anstieg zu verzeichnen. Eine Ausnahme war hier die obersten 5 cm des Profils einer Überschwemmungsebene auf der Insel Samoylov. Hier war Methanol das bevorzugte Substrat. Die Erhöhung der Temperatur hatte ebenfalls einen positiven Einfluss auf die Methanbildungsrate. Es ließ sich allerdings kein einheitliches Muster in der Methanbildungsaktivität der methanogenen Archaeen für die unterschiedlichen Bodentypen nachweisen. Für alle Profile gemeinsam war, dass eine zum Teil sehr hohe Methanbildungsrate von bis zu 270 nmol CH4 h-1 g-1 mit H2/CO2 als Substrat für die obersten 10 cm festzustellen war. Mit zunehmender Tiefe änderte sich das Bild. Während die Aktivität im Polygonzentrum des Standortes Kap Mamontovy Klyk stark abnahm, gab es ein zweites Aktivitätsmaximum in der Überschwemmungsebene der Insel Samoylov in der Zone der stärksten Durchwurzelung. Das untersuchte Polygonzentrum der Insel Samoylov zeigte ebenfalls ein zweites Aktivitätsmaximum, allerdings lag dieses in der Zone dicht über dem Permafrost. Nach Analyse der Aktivitätstests, die bei verschiedenen Temperaturen und mit unterschiedlichen Substraten durchgeführt wurden, konnte bereits die Schlussfolgerung gezogen werden, dass sich die Gemeinschaft der methanogenen Archaeen in den verschiedenen Bodenhorizonten voneinander unterscheidet. Es wurde außerdem angenommen, dass die Diversität mit der Tiefe abnimmt, hervorgerufen durch die abnehmende Temperatur und den sinkenden Gehalt an organischem Kohlenstoff. Dies wurde durch die Ergebnsisse der Denaturierenden Gradienten-Gelelektrophorese (DGGE) nur teilweise bestätigt. Die Diversität nahm mit zunehmender Tiefe in der Auftauschicht erst zu und erreichte ihre größte Vielfalt in der Mitte der untersuchten Bodenprofile, um dann stark abzunehmen. Eine Ausnahme bildete die Überschwemmungsebene. Hier war die Diversität der methanogenen Mikroorganismen über das gesamte Profil etwa gleichbleibend. In allen der untersuchten arktischen Böden konnten Vertreter der Ordnung Methanomicrobiales und der Gattung Methanosarcina nachgewiesen werden. Desweiteren wurden auch Vertreter der Familie Methanosaetaceae gefunden, allerdings nur für die Überschwemmungsebene und das Polygonzentrum der Insel Samoylov. Die aus den Ergebnissen gezogenen Schlüsse lassen die Annahme zu, dass es in diesen Habitaten psychrophile bzw. psychrotolerante methanogene Mikroorganismen gibt, die optimal an die dort herrschenden, extremen klimatischen Bedingungen angepasst sind. Dies wird durch die Tatsache gestützt, dass es bereits einige psychrophile bzw. psychrotolerante Isolate von methanogenen Archaeen gibt.

Description: Hydromorphic arctic tundra soils are a very important source of atmospheric methane (CH4) which is according to CO2 the most climate relevant greenhouse gas.Wet tundra environments are generally a net carbon sink since the predominant environmental conditions reduce decomposition of organic matter and support a carbon accumulation. More than 14 % of the global terrestrial carbon is stored in soils and sediments of Arctic permafrost environments.Most of the climate models predict a global warming for the next century, which will be shown in deeper and longer thaw processes in the active layer of permafrost soils in the High Arctic and probably of a higher rate of degradation of organic matter and emission of methane and carbon dioxide.The microbial methane production (methanogenesis) is one of the most prominent microbiological processes during the anaerobic decomposition of organic matter. A group of strictly anaerobic organisms called methanogenic archaea is responsible for methanogenesis. The methanogenic archaea use the metabolism end products of bacteria involved in the anaerobic foodchain, which transform complex organic molecules into simple compounds like H2, CO2, acetate, formiate.After its production methane is partly oxidized either in the aerobic top layer of permafrost soils or in the aerobic rhizosphere by highly specialized Proteobacteria, belonging to the group of methanotrophic bacteria. They are using CH4 as the sole carbon source, while energy is gained by the oxidation of CH4 to CO2.In this study the community structure of methanogenic archaea was analyzed by polymerase chain reaction (PCR) using a nested primer approach with two different internal primer sets following denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene fragments. These modern molecular ecological methods allow to study the microbial community including uncultivable microorganisms.To investigate the archaeal community structure samples from three geomorphological different sites were taken:(i) a low centre polygon, (ii) a floodplain (both sites are located on Samoylov Island, Lena Delta) and (iii) a thermoerosion valley (Cape Mammontovy Klyk, ca. 400 km northwest of Samoylov). DNA was extracted directly from soils or from enrichment cultures. Samples for enrichment were taken from two different depths and were incubated under different conditions concerning temperature, salt content and substrates.The comparsion of the three different habitats showed clear differences between the composition of the methanogenic Archaea in the different environments. Both places on Samoylov showed a higher diversity than samples from Mammontovy Klyk. Results also indicate that there is a shift in the community structure from the top to the bottom of the active layer.The DGGE method is a very useful tool to get a fast overview about the composition of microbial communities in complex habitats. It can be also used to controll the enrichment and isolation of pure bacterial cultures.But nevertheless for detailed information about the methanogenic diversity the construction of a clone libary should be the next aim.

Description: The microbial CH4 production (methanogenesis) is one of the most prominent microbiological processes in wet terrestrial environments. During the anaerobic decomposition of complex organic matter, CH4 is formed by using metabolism end products of bacteria involved in the anaerobic foodchain (e.g. H2, CO2, acetate, formate). Here we analyzed the community structure of methanogenic archaea in arctic tundra soils by PCR using a specific primer set following DGGE and sequencing of 16S rRNA gene fragments. For the investigation of the methanogenic community composition we took samples from three different sites: (i) a low centre polygon, (ii) a floodplain (both sampling sites are located on Samoylov Island, Lena Delta) and (iii) a thermoerosion valley (Cape Mammontovy Klyk, ca. 400 km northwest the Lena Delta). DNA was extracted directly from soil using a commercial kit. First results showed both differences and similarities in the community structure of the three habitats. The banding patterns display the diversity of the methanogenic archaea which seems to be higher on Samoylov Island than at the sampling site of Mammontovy Klyk. It also seems that there are some methanogenes that probably can be found at any of the sampling sites.With increasing depth of the active layer, and thus decreasing temperature, the vertical profile of the microorganisms changed. However, the pattern also showed that some organisms were located both in the top layer and in the zone near the permafrost. Influence on the change of the methanogenic community could also have thawing-freezing processes or the variety of utilisable substrates.