Center for Geomicrobiology

Århus, Denmark

Center for Geomicrobiology

Århus, Denmark
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Croese E.,Wageningen University | Croese E.,Center of Excellence for Sustainable Water Technology | Jeremiasse A.W.,Center of Excellence for Sustainable Water Technology | Jeremiasse A.W.,Wageningen University | And 9 more authors.
Enzyme and Microbial Technology | Year: 2014

The microbial electrolysis cell (MEC) biocathode has shown great potential as alternative for expensive metals as catalyst for H2 synthesis. Here, the bacterial communities at the biocathode of five hydrogen producing MECs using molecular techniques were characterized. The setups differed in design (large versus small) including electrode material and flow path and in carbon source provided at the cathode (bicarbonate or acetate). A hydrogenase gene-based DNA microarray (Hydrogenase Chip) was used to analyze hydrogenase genes present in the three large setups. The small setups showed dominant groups of Firmicutes and two of the large setups showed dominant groups of Proteobacteria and Bacteroidetes. The third large setup received acetate but no sulfate (no sulfur source). In this setup an almost pure culture of a Promicromonospora sp. developed. Most of the hydrogenase genes detected were coding for bidirectional Hox-type hydrogenases, which have shown to be involved in cytoplasmatic H2 production. © 2014 Elsevier Inc.

Barcena T.G.,University of Aarhus | Finster K.W.,University of Aarhus | Finster K.W.,Max Planck Institute for Marine Microbiology | Yde J.C.,University of Aarhus | And 3 more authors.
Arctic, Antarctic, and Alpine Research | Year: 2011

Increasing global annual temperature leads to massive loss of ice cover worldwide. Consequently, glaciers retreat and ice-covered areas become exposed. We report on a study from the Mittivakkat Gletscher forefield in Southeast Greenland with special focus on methanotrophy in relation to exposure time to the atmosphere. The Mittivakkat Gletscher has receded since the end of the Little Ice Age (LIA; about AD 1850) and has left behind a series of deposits of decreasing age concurrently with its recession. Soil samples from this chronosequence were examined in order to elucidate main soil variables, as well as the activity and community structure of methanotrophs, a group of microorganisms involved in regulation of atmospheric methane. Soil variables revealed poor soil development, and incubation experiments showed methane consumption rates of 2.14 nmol CH4 day-1 gsoil-1 at 22 °C and 1.24 nmol CH4 day-1 gsoil-1 at 10 °C in the LIA terminal moraine. Methane consumption was not detected in younger samples, despite the presence of high-affinity methanotrophs in all samples. This was indicated by successful amplification of partial pmoA genes, which code for a subunit of a key enzyme involved in methane oxidation. In addition, the results of the diversity study show that the diversity of the methanotrophic community at the younger, recently deglaciated site P5 is poorer than the diversity of the community retrieved from the LIA moraine. We put forward the hypothesis that aerobic methanotrophs were at very low abundance and diversity during glaciation probably due to anoxia at the ice-sediment interface and that colonization after deglaciation is not completed yet. More detailed studies are required to explain the causes of discrepancy between activity and presence of high-affinity methanotrophs and its relation to the transit from ice-covered probably anoxic to ice-free oxic conditions. © 2011 Arctic, Antarctic, and Alpine Research.

Finster K.W.,University of Aarhus | Kjeldsen K.U.,Center for Geomicrobiology | Kube M.,MPI Molecular Genetics | Reinhardt R.,MPI Molecular Genetics | And 3 more authors.
Standards in Genomic Sciences | Year: 2013

Desulfocapsa sulfexigens SB164P1 (DSM 10523) belongs to the deltaproteobacterial family Desulfobulbaceae and is one of two validly described members of its genus. This strain was selected for genome sequencing, because it is the first marine bacterium reported to thrive on the dispropor-tionation of elemental sulfur, a process with a unresolved enzymatic pathway in which elemental sulfur serves both as electron donor and electron acceptor. Furthermore, in contrast to its phylogenetically closest relatives, which are dissimilatory sulfate-reducers, D. sulfexigens is unable to grow by sulfate reduction and appears metabolically specialized in growing by disproportionating elemental sulfur, sulfite or thiosulfate with CO2 as the sole carbon source. The genome of D. sulfexigens contains the set of genes that is required for nitrogen fixation. In an acetylene assay it could be shown that the strain reduces acetylene to ethylene, which is indicative for N-fixation. The circular chromosome of D. sulfexigens SB164P1 comprises 3,986,761 bp and harbors 3,551 protein-coding genes of which 78% have a predicted function based on auto-annotation. The chromosome furthermore encodes 46 tRNA genes and 3 rRNA operons.

News Article | March 2, 2017

On Friday, The Association for the Sciences of Limnology and Oceanography (ASLO) honors Danish Professor Bo Barker Jørgensen with the prestigious 2017 A.C. Redfield Award at the Aquatic Sciences Meeting in Honolulu, Hawaii 26 February - 03 March, 2017. Dr. Bo Barker Jørgensen receives the prize for his lifelong and groundbreaking work advancing our understanding of marine sediment microbial ecology and biogeochemistry. His work has ranged from surface sediments to the deep biosphere, several kilometers into the seabed. ASLO is an international aquatic science society founded in 1948. For more information about ASLO, please visit their website: http://www. . In their press release, ASLO writes, "Bo Barker Jørgensen has led the way in advancing our understanding of the biogeochemistry and microbial ecology of marine sediments. His papers have been cited more than 32,000 times, with two of his papers having over one thousand citations each. Colleagues say these statistics are evidence of Jørgensen's "jaw dropping" influence on science and a tribute to the huge impact of his lifelong work." ASLO also highlights Bo Barker Jørgensen's early research on the sulfur cycle in marine sediments presented in a paper in 1977. The method he developed for determining the rate of bacterial sulfate reduction in marine sediments is still in use today and his paper is of one of the most highly cited papers in marine sediment biogeochemistry. Another highlight in a long and illustrious science career is the work of Bo Barker Jørgensen and then graduate student, Niels Peter Revsbech who is now a professor and colleague at Aarhus University, Denmark. During the late 70's and early 80's they used oxygen microelectrodes for the first time to measure the distribution of oxygen in sediments, "...shocking the scientific community with their discovery that oxygen penetrates only a few millimeters into coastal sediments. Their introduction of microelectrodes revolutionized our understanding of the distribution and dynamics of oxygen and oxidants in marine sediments," ASLO writes in their nomination. Bo Barker Jørgensen is famous not only for developing techniques, instruments and publishing influential papers, but the A. C. Redfield award also recognizes his work achievements as a mentor. Many of the young scientists he advised have established successful scientific careers of their own. "The list of students, postdoctoral fellows and colleagues who have been mentored by Jørgensen reads like a virtual 'who's who' of marine microbiology," the nomination reads. Bo Barker Jørgensen's vision for microbial research is credited by colleagues as central for the establishment of Max Planck Institute for Marine Microbiology in Bremen, Germany. Bo Barker Jørgensen served as director of the Institute from 1992-2011, and helped to establish it as a world leader in research on marine microbes. In 2007, Bo Barker Jørgensen established the Center for Geomicrobiology in Aarhus, where he has built an international team of leading scientists focused on sediments in the deep biosphere. "He and his team are 'providing fundamental and new insights into the nature of what may be the largest, yet least known, biosphere on Earth,'" it is written in the nomination. Contact: Bo Barker Jørgensen is at the moment in Hawaii but can be reached on mail: The ASLO Lifetime Achievement award is given to those that have excelled in limnologic and oceanographic research, education, service to the community and society throughout a lifetimes work. The prize was first presented in 1994 and has since 2004 been named after Alfred Clarence Redfield, an American oceanographer whose major discovery was the atomic ratio between nitrogen, phosphorus, and carbon found in marine plankton (phytoplankton), also known as the Redfield ratio. Dr. Jørgensen is Professor and Head of the Center for Geomicrobiology at Aarhus University in Denmark. In his long career, Bo Barker Jørgensen has received numerous prizes and honors for his impressive work: Fellow of the American Academy of Microbiology, 2009 Fellow of the European Academy of Microbiology, 2009

Capek P.,University of South Bohemia | Diakova K.,University of South Bohemia | Dickopp J.-E.,University of Ulm | Barta J.,University of South Bohemia | And 29 more authors.
Soil Biology and Biochemistry | Year: 2015

Arctic permafrost soils contain large stocks of organic carbon (OC). Extensive cryogenic processes in these soils cause subduction of a significant part of OC-rich topsoil down into mineral soil through the process of cryoturbation. Currently, one-fourth of total permafrost OC is stored in subducted organic horizons. Predicted climate change is believed to reduce the amount of OC in permafrost soils as rising temperatures will increase decomposition of OC by soil microorganisms. To estimate the sensitivity of OC decomposition to soil temperature and oxygen levels we performed a 4-month incubation experiment in which we manipulated temperature (4-20 °C) and oxygen level of topsoil organic, subducted organic and mineral soil horizons. Carbon loss (CLOSS) was monitored and its potential biotic and abiotic drivers, including concentrations of available nutrients, microbial activity, biomass and stoichiometry, and extracellular oxidative and hydrolytic enzyme pools, were measured. We found that independently of the incubation temperature, CLOSS from subducted organic and mineral soil horizons was one to two orders of magnitude lower than in the organic topsoil horizon, both under aerobic and anaerobic conditions. This corresponds to the microbial biomass being lower by one to two orders of magnitude. We argue that enzymatic degradation of autochthonous subducted OC does not provide sufficient amounts of carbon and nutrients to sustain greater microbial biomass. The resident microbial biomass relies on allochthonous fluxes of nutrients, enzymes and carbon from the OC-rich topsoil. This results in a "negative priming effect", which protects autochthonous subducted OC from decomposition at present. The vulnerability of subducted organic carbon in cryoturbated arctic soils under future climate conditions will largely depend on the amount of allochthonous carbon and nutrient fluxes from the topsoil. © 2015 Elsevier Ltd.

Wild B.,University of Vienna | Wild B.,Austrian Polar Research Institute | Wild B.,Gothenburg University | Schnecker J.,University of Vienna | And 15 more authors.
Global Biogeochemical Cycles | Year: 2015

Soil N availability is constrained by the breakdown of N-containing polymers such as proteins to oligopeptides and amino acids that can be taken up by plants and microorganisms. Excess N is released from microbial cells as ammonium (N mineralization), which in turn can serve as substrate for nitrification. According to stoichiometric theory, N mineralization and nitrification are expected to increase in relation to protein depolymerization with decreasing N limitation, and thus from higher to lower latitudes and from topsoils to subsoils. To test these hypotheses, we compared gross rates of protein depolymerization, N mineralization and nitrification (determined using 15N pool dilution assays) in organic topsoil, mineral topsoil, and mineral subsoil of seven ecosystems along a latitudinal transect in western Siberia, from tundra (67°N) to steppe (54°N). The investigated ecosystems differed strongly in N transformation rates, with highest protein depolymerization and N mineralization rates in middle and southern taiga. All N transformation rates decreased with soil depth following the decrease in organic matter content. Related to protein depolymerization, N mineralization and nitrification were significantly higher in mineral than in organic horizons, supporting a decrease in microbial N limitation with depth. In contrast, we did not find indications for a decrease in microbial N limitation from arctic to temperate ecosystems along the transect. Our findings thus challenge the perception of ubiquitous N limitation at high latitudes, but suggest a transition from N to C limitation of microorganisms with soil depth, even in high-latitude systems such as tundra and boreal forest. ©2015. The Authors.

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