Existing models of soil organic matter (SOM) formation consider plant material as the main source of SOM. Recent results from nuclear magnetic resonance analyses of SOM and from own incubation studies, however, show that microbial residues also contribute to a large extent to SOM formation. Scanning electron microscopy showed that the soil mineral sur-faces are covered by numerous small patchy fragments (100 - 500 nm) deriving from microbial cell wall residues. We will study the formation and fate of these patchy fragments as continuously produced interfaces in artificial soil systems (quartz, montmorillonite, iron oxides, bacteria and carbon sources). We will quantify the relative contributions of different types of soil organisms to patchy fragment formation and elucidate the effect of redox con-ditions and iron mineralogy on the formation and turnover of patchy fragments. The develop-ment of patchy fragments during pedogenesis will be followed by studying soil samples from a chronosequence in the forefield of the retreating Damma glacier. We will characterize chemical and physical properties of the patchy fragments by nanothermal analysis and microscale condensation experiments in an environmental scanning electron microscope. The results will help understanding the processes at and characteristics of biogeochemical interfaces.
Arsenic-contaminated ground- and drinking water is a global environmental problem with about 1-2Prozent of the world's population being affected. The upper drinking water limit for arsenic (10 Micro g/l) recommended by the WHO is often exceeded, even in industrial nations in Europe and the USA. Chronic intake of arsenic causes severe health problems like skin diseases (e.g. blackfoot disease) and cancer. In addition to drinking water, seafood and rice are the main reservoirs for arsenic uptake. Arsenic is oftentimes of geogenic origin and in the environment it is mainly bound to iron(III) minerals. Iron(III)-reducing bacteria are able to dissolve these iron minerals and therefore release the arsenic to the environment. In turn, iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II)- oxidation at neutral pH followed by iron(III) mineral precipitation. This process may reduce arsenic concentrations in the environment drastically, lowering the potential risk for humans dramatically.The main goal of this study therefore is to quantify, identify and isolate anaerobic and aerobic Fe(II)-oxidizing microorganisms in arsenic-containing paddy soil. The co-precipitation and thus removal of arsenic by iron mineral producing bacteria will be determined in batch and microcosm experiments. Finally the influence of rhizosphere redox status on microbial Fe oxidation and arsenic uptake into rice plants will be evaluated in microcosm experiments. The long-term goal of this research is to better understand arsenic-co-precipitation and thus arsenic-immobilization by iron(II)-oxidizing bacteria in rice paddy soil. Potentially these results can lead to an improvement of living conditions in affected countries, e.g. in China or Bangladesh.
In der Arbeit wurden die Faelle des gehaeuften Auftretens von Crenothrix polyspora zusammengefasst, die morphologischen Untersuchungen erneut aufgenommen und durch elektronenmikroskopische Aufnahmen von dritter Seite ergaenzt. Ferner wurden weitere Beobachtungen zur Beschreibung des Mikroorganismus gegeben und letztlich wird auf die Moeglichkeit zur Kultur von Crenothrix eingegangen. Unter natuerlichen Bedingungen findet eine Massenvermehrung von Crenthrix polyspora dann statt, wenn sich ein durch das Eindringen von abbaubarer organischer Substanz sauerstofffrei gewordenes Grundwasser mit sauerstoffreichem und somit nitrathaltigen Wasser anderer Herkunft mischt. Diese Mischung tritt ein, wenn das Wasser fuer die Trinkwassergewinnung an die Oberflaeche gepumpt wird. Die sich insgesamt abspielenden chemischen und mikrobiologisch-chemischen Reaktionen sind in den Abbildungen 44a, b, c, zusammengefasst. Sie reichen insgesamt gesehen jedoch nicht aus, um die Bedingungen der Massenvermehrung von Crenothrix polyspora praezise zu definieren.
Seit 1964 werden im Auftrag von Wasserwerken mikrobiologische und chemische Untersuchungen zur Uferfiltration im Rahmen von Trinkwasserversorgungsanlagen durchgefuehrt. Wird ein Uferfiltrat infolge zu grosser Belastung mit organischer Substanz anaerob, so entstehen mikrobiologische und chemische Produkte, die ihrerseits nach Mischung dieses Wassers mit sauerstoffhaltigen Hangwasser wiederum oxydiert werden und zur Massenvermehrung von Mikroorganismen fuehren.
In freshwater sediments, iron oxidation is dominated by phototrophic and chemotrophic (aerobic and nitrate-reducing) Fe(ll)-oxidizing microorganisms. Although these biogeochemical processes have been investigated in detail in laboratory studies, not much is known about their spatial distribution, interactions (e.g. competition) amongst each other, as well as their response towards environmental perturbations (i.e. temperature, geochemical variations (nutrient, organic matter input)). This research proposal aims to investigate the activity, abundance and resource competition between different chemotrophic (aerobic and (autotrophic/mixotrophic) anaerobic nitrate-reducing) and phototrophic ironoxidizing microorganisms. In order to better understand the spatial distribution of nitrate-reducing iron oxidizing bacteria, microbial nitrate-producing and competing, nitrate-depletion processes will also be studied throughout the sedimentary redox gradient. In addition, the activity and abundance of the ironoxidizing processes will be quantified with (geo)microbiological, molecular and novel spectral imaging techniques. Using high resolution geochemical measurements (microsensors) we will characterize the environmental conditions these bacteria experience in order to determine the role of spatial and functional niche competition in microbial iron oxidation and the interconnection to the N-cycle. Iron mineral formation will be investigated as a function of the microbial spatial and temporal activity, depending on environmental perturbations. The proposed research study will strongly improve the understanding of iron cycling, the interconnection to the N-cycle, as well as interactions and competition between phototrophic and chemotrophic metabolisms in aquatic environments.
Grundwässer können durch äußere Kontamination, zum Beispiel in Folge von Starkregen, Überschwemmungen oder raschen Kurzschlüssen mit Oberflächengewässern mit hygienisch relevanten Mikroorganismen verunreinigt werden. Beim Transport im Grundwasser können solche Mikroorganismen Brunnen der Trinkwassergewinnung erreichen. Liegt dort eine Inkrustierung vor, meist in Form von Eisen(III)-oxiden bzw. -oxyhydroxiden (Brunnenverockerung), wird den Organismen eine sehr große und poröse Oberfläche zur Ansiedlung geboten. Ziel des Projektes ist die Klärung folgender Fragen: - Kann bei Vorliegen einer Verockerung diese Matrix als Lebensraum dienen? - Können sich hygienisch relevante Mikroorganismen einnisten, halten, vermehren? - Und wenn ja, wie können diese am wirksamsten und nachhaltigsten bekämpft werden? Hierzu werden Realproben verockerter Brunnen auf das Vorkommen hygienisch relevanter Mikroorganismen untersucht, wobei neben Kulturmethoden vor allem auch kulturunabhängige Verfahren (FISH, PCR-basierte Methoden) eingesetzt werden. In Laborsystemen soll die Verockerung nachgestellt werden und durch definierte Beaufschlagung mit den Zielorganismen (Escherichia coli, intestinale Enterokokken, coliforme Bakterien, Legionella pneumophila, Pseudomonas aeruginosa, Aeromonas spp.) deren Einnistung, Persistenz und mögliches Wachstum untersucht werden. Die Effektivität von Sanierungsverfahren, speziell unter Einsatz von Wasserstoffperoxid, soll geprüft werden.
Iron reduction in subseafloor sulfate-depleted and methane-rich marine sediments is currently a subject of interest in subsurface geomicrobiology. While iron reduction and microorganisms involved have been well studied in marine surface sediments, little is known about microorganisms responsible for iron reduction in deep methanic sediments. Here, we used quantitative PCR (Q-PCR)-based 16S rRNA gene copy numbers and pyrosequencing-based relative abundances of bacteria and archaea to investigate covariance between distinct microbial populations and specific geochemical profiles in the top 5 m of sediment cores from the Helgoland mud area, North Sea. We found that gene copy numbers of bacteria and archaea were specifically higher around the peak of dissolved iron in the methanic zone (250-350 cm. The higher copy numbers at these depths were also reflected by the relative sequence abundances of members of the candidate division JS1, methanogenic and Methanohalobium/ANME-3 related archaea. The distribution of these populations was strongly correlated to the profile of pore-water Fe2+ while that of Desulfobacteraceae corresponded to the pore-water sulfate profile. Furthermore, specific JS1 populations also strongly co-varied with the distribution of Methanosaetaceae in the methanic zone. Our data suggest that the interplay among JS1 bacteria, methanogenic archaea and Methanohalobium/ANME-3-related archaea may be important for iron reduction and methane cycling in deep methanic sediments of the Helgoland mud area and perhaps in other methane-rich depositional environments. .
Despite the high production of the greenhouse gas methane in ocean and ocean sediments, only 2% of the gas finally reaches the atmosphere. Specialized bacteria in the ocean use methane as their source of carbon and energy and, hence, are thought to maintain nanomolar methane concentrations in the bulk of the ocean. The proposed project aims to investigate different chemical, biological, and physical factors that enhance or limit microbial methane oxidation as an important sink of methane in the ocean. For example, often low methane oxidation rates have been found in surface waters, which may be caused by copper and/or iron limitation or light inhibition of methane oxidizing bacteria. In addition, methane as substrate for the bacteria may be limited due to increased sea surface air gas exchange by increased wind speed. In contrast, high methane oxidation rates have been measured in bottom water of coastal basins with limited water exchange. These high oxidation rates often correlate with lower oxygen concentrations and/or increased suspended material content in the surrounding water. Field studies in different climatic zones (polar: Spitsbergen and Antarctica, subtropical: Santa Barbara Basin, tropical: Gulf of Mexico) in combination with laboratory experiments are planned to study factors enhancing and limiting microbial methane oxidation in the ocean. Mainly the process of methane oxidation will be investigated by using radioactive tracers and stable carbon isotopes. Thereby maximum uptake rates of in situ methane oxidizing bacterial communities will be measured at different conditions. Finally, the results of the field and laboratory studies will be combined to develop a box model that can be used to estimate and possibly predict aerobic methane oxidation, one of the important methane sinks in the ocean.
1. Kurzfassung: In diesem Projekt sollen erstmals die Existenz und das Potenzial von relevanten Bakteriengruppen in einer existierenden reaktiven Wand mit elementarem Eisen erfasst werden. Ein Hauptziel dieses Forschungsvorhabens ist es, den Einfluss von Mikroorganismen auf das Langzeitverhalten reaktiver Systeme mit Fe0 zu untersuchen. Dabei soll zum einen festgestellt werden, ob verschiedene, fuer bestimmte Grundwaesser typische Mikroorganismen faehig sind, elementares Eisen dauerhaft zu besiedeln und ob dadurch signifikante Permeabilitaetsverluste und Leistungseinbussen des reaktiven Systems entstehen. Zum anderen soll ueberprueft werden, ob und wie die Dechlorierungscharakteristik eines reaktiven Systems mit Fe0 durch verschiedene Mikroorganismengruppen beeinflusst wird. 2. Arbeitsplanung: eingeteilt in 2 Phasen; Details siehe Antrag 3. Ergebnisverwertung: Wenn es in der zweiten Haelfte der beantragten Foerderphase zu weitergehenden Versuchen zur Bioaugmentation von Fe0 reaktiven Systemen kommen sollte, ergibt sich daraus eventuell die Moeglichkeit innovative Verfahrensvarianten abzuleiten. In diesem Fall sollen die erzielten Ergebnisse auf ihre Patentfaehigkeit geprueft werden.
Laboratory experiments were performed to elucidate the chemical and microbial reduction (dissolution) rates of iron(hydr)oxides in the neutral (natural) pH range. Results revealed that cysteine, a model reductant for bacterial Fe reducing enzymes, applied in the millimolar concentration range, reduced 2-line ferrihydrite much faster in the first 24 hours than did 3 108 cells/mI of the bacterium Shewanella alga, Geobacter sulfurreducens and Geobacter metamreducens (GS-15). The rates measured were 600 and 0.6-4 nmol /min m2, respectively. For goethite, the initial abiotic and biotic dissolution rates stayed in the same range, 4 and 2 - 3 nmol /min m2, respectively. lnitial reduction rates varied little between the different bacteria and iron(hydr)oxides, if calculated per surface area of the oxides. They also depended relatively weakly on the number of bacteria present. The chemical reductive dissolution rate was controlled by the concentration of the surface complex of cysteine at the iron(hydr)oxide. In microbial growth experiments, lasting 7 to 15 weeks, initial dissolution rates decreased to 0.1 to 0.7 nmol /min m2 only, although the culture media contained 4 mM phosphate. After 5 to 10 weeks reduction rates diminished drastically since magnetite was formed that is known to be not available for iron reducers and in addition the iron(hydr)oxide coagulated to larger particles. Phosphate in the millimolar concentration range lowered the chemical reduction rate with cysteine more than one order of magnitude.
| Origin | Count |
|---|---|
| Bund | 27 |
| Wissenschaft | 1 |
| Type | Count |
|---|---|
| Förderprogramm | 27 |
| Strukturierter Datensatz | 1 |
| License | Count |
|---|---|
| offen | 28 |
| Language | Count |
|---|---|
| Deutsch | 17 |
| Englisch | 11 |
| Resource type | Count |
|---|---|
| Archiv | 1 |
| Keine | 13 |
| Webseite | 14 |
| Topic | Count |
|---|---|
| Boden | 21 |
| Lebewesen & Lebensräume | 28 |
| Luft | 14 |
| Mensch & Umwelt | 28 |
| Wasser | 26 |
| Weitere | 27 |