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Biogeochemistry Group

Congratulations to Nadine Lehnen and Alexander Khachikyan, who successfully defended their PhD-Theses (3/13/2020).

 

Congratulations to one of the pioneers of the Biogeochemistry Group, our technician Swant­je Li­li­en­thal...
... on her 25 year anniversary! We are looking forward to the next years.

 

Carbon and Nutrient Cycles (c) Soeren Ahmerkamp

Research in the Biogeochemistry Group focuses on microbiological and geochemical processes that control bioactive element cycling in the marine environment. We employ geochemical, microbiological, modeling, molecular and single-cell techniques to study the environmental regulation of these processes, and their effects on the global biogeochemical cycles.

Our goal is to provide fundamental insights into microbial mediated processes in the Ocean that ultimately affect Ocean chemistry, biology and climate, and vital input for models used to predict potential future changes resulting from human activities.

Recent Publications

24. March 2020

New in Scientific Reports: Golf ball-like sand grains provide ideal structures for microbial colonization

Sandy sediments cover more than 50% of the continental shelf and are akin to biocatalytic-filters, remineralizing carbon and removing nutrients at very high rates. Despite the growing awareness of the importance of sandy sediments in marine nutrient cycling, little is known about the factors that control carbon and nutrient turnover. In a recent publication in Scientific Reports (Link), we show that the surface area of a sand grain that is available for colonization is key to the regulation of bacterial cell numbers and therefore the regulation of respiration rates. Surprisingly, sand grains with a golf-ball like structure are ideal for microbial colonization by providing protective structures, but also by ensuring an optimal solute supply. 

11. November 2019

New in AEM: Chemolithoheterotrophy by a Novel Arcobacter Species Isolated from the Sulfide-Rich Waters off Peru

Denitrifying and micro-aerophilic bacterial communities that oxidize sulfide to elemental sulfur are commonly associated with sulfidic coastal bottom waters in upwelling regions such as Peru. In a recent paper in Applied and Environmental Microbiology [Callbeck et al., 2019, Arcobacter peruensis sp.nov., a chemolithoheterotroph isolated from sulfide and organic rich coastal waters off Peru. https://aem.asm.org/content/early/2019/10/01/AEM.01344-19] former MPI Biogeochemistry doctoral student, Cameron Callbeck and colleagues from MPI, Radboud University, Nijmengen and GEOMAR Kiel isolated a novel Arcobacter species from the sulfide- and organic matter-rich waters of the Peruvian shelf. The isolate, named Arcobacter peruensis, was capable of sulfide oxidation and nitrate reduction, but is incapable of autotrophic CO2 fixation, unlike other sulfide-oxidizing denitrifiers, such as UThioglobus peridus (from the SUP05 clade). Instead, Arcobacter peruensis depends on organic matter for growth on sulfide and nitrate. The favorable growth efficiencies of this chemolithoheterotrophic metabolism might explain why Arcobacter peruensis is able to rapidly bloom in the sulfide-rich waters off Peru.

Our multidisciplinary approach involved extensive shipboard sampling and experimentation during the Meteor M93 expedition to the Eastern Tropical South Pacific near Peru. Further  nanoSIMS imaging and pure culturing approaches, were employed to elucidate the ecophysiology of this environmental Arcobacter species. The paper provides insights into the physiological flexibility of the Arcobacter genus and sulfide-oxidizing, denitrifying microbial communities within oceanic oxygen minimum zones. Arcobacter peruensis may play a substantial role in the diverse consortium of bacteria that is capable of coupling denitrification and fixed nitrogen loss to sulfide oxidation in eutrophic, sulfidic coastal waters. With increasing anthropogenic pressures on coastal regions, e.g. eutrophication and deoxygenation (D. Breitburg, et al., Science 359:eaam7240, 2018 DOI: 10.1126/science.aam7240), niches where sulfide-oxidizing, denitrifying heterotrophs such as A. peruensis thrive are likely to expand.

3. June 2019

Key players in the marine nitrogen cycle can utilize cyanate and urea

The ammonia oxidizing archaea, or Thaumarchaeota, are amongst the most abundant marine microorganisms. Yet, we are still discovering which factors allow them to thrive in the ocean: A new publication reveals that marine Thaumarchaeota have a broader metabolism than previously thought and utilize cyanate and urea as alternative substrates. https://www.nature.com/articles/s41564-018-0316-2

24. October 2018

N2O-emmisions from coastal sandy sediments

In a study recently published in Environmental Microbiology (https://onlinelibrary.wiley.com/doi/epdf/10.1111/1462-2920.14385), H. Marchant and col­le­agues describe how the microbial community and highly variable conditions in sandy sediments can drive substantial emissions of the potent greenhouse gas, nitrous oxide (N2O). They reveal that different steps of denitrification appear to be carried out by distinct members of the community, in particular, the microorganisms that produce N2O, differ from the microorganisms that are consuming N2O. Therefore N2O is released into the porewater of the sediment, and a fraction of the dissolved gas is then transported into the water column and released to the atmosphere. Sandy sediments cover up to 50 % of the continental shelves and form an integral part of the land-ocean continuum, but in the past, research into the biogeochemistry and microbiology of sands has been lacking. The current paper forms part of our ongoing research into these fascinating hotspots.

H. Marchant collecting water column samples
H. Marchant collecting water column samples at the Janssand sandflat as part of the study, and the same location 7 hours later.

10. July 2018

New insights into the evolutionary history of nitrification

In a new stu­dy pu­blis­hed in the jour­nal mbio (http://mbio.asm.org/content/9/4/e01186-18), K. Kitzinger and col­le­agues from University of Vienna (Austria), Radboud University (The Netherlands), Aalborg University (Denmark) and the MPI for Marine Microbiology describe the first pure culture of the nitrite oxidizing genus Nitrotoga, N. fabula, its physiological and genomic potential, and reveal a novel nitrite oxidizing enzyme, which expands the picture of the evolutionary history of nitrification and hints at the possibility of archaeal nitrite oxidizers.

20. June 2018

Novel methane oxidizer from a stratified lake

A new study published in the journal Environmental Microbiology by J. GrafJ. Milucka and colleagues reports on the abundance, genomic potential and functional gene transcription of a blooming denitrifying methanotroph, "Ca. Methylomirabilis limnetica", from a deep stratified freshwater lake.

 

14. June 2018

The microbial nitrogen cycling network

A comprehensive review by M. Kuypers, H. Marchant and B. Kartal has been published in Nature Reviews Microbiology. This Review summarizes our current understanding of the microbial nitrogen-cycling network, including novel processes, their underlying biochemical pathways, the involved microorganisms, their environmental importance and industrial applications.

Nitrogen loss from freshwater reservoirs

A new study published in the journal Nature Communications by Dr. Wajih Naqvi (CSIR) and colleagues shows that methane accumulation in anoxic freshwater systems seems to facilitate rapid loss of reactive nitrogen. M. Kuypers and G. Lavik were involved in this work. See full MPI press release HERE.

 
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