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  • PANGAEA  (884)
  • BioMed Central  (353)
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  • 1
    Publication Date: 2024-03-06
    Description: Eastern boundary upwelling systems (EBUS) are among the most productive marine ecosystems on Earth. The production of organic material is fueled by upwelling of nutrient-rich deep waters and high incident light at the sea surface. However, biotic and abiotic factors can mod- ify surface production and related biogeochemical processes. Determining these factors is important because EBUS are considered hotspots of climate change, and reliable predic- tions of their future functioning requires understanding of the mechanisms driving the biogeochemical cycles therein. In this field experiment, we used in situ mesocosms as tools to improve our mechanistic understanding of processes con- trolling organic matter cycling in the coastal Peruvian up- welling system. Eight mesocosms, each with a volume of ∼ 55 m3, were deployed for 50 d ∼ 6 km off Callao (12◦ S) during austral summer 2017, coinciding with a coastal El Niño phase. After mesocosm deployment, we collected sub- surface waters at two different locations in the regional oxy- gen minimum zone (OMZ) and injected these into four meso- cosms (mixing ratio ≈ 1.5 : 1 mesocosm: OMZ water). The focus of this paper is on temporal developments of organic matter production, export, and stoichiometry in the indi- vidual mesocosms. The mesocosm phytoplankton commu- nities were initially dominated by diatoms but shifted to- wards a pronounced dominance of the mixotrophic dinoflag- ellate (Akashiwo sanguinea) when inorganic nitrogen was exhausted in surface layers. The community shift coincided with a short-term increase in production during the A. san- guinea bloom, which left a pronounced imprint on organic matter C : N : P stoichiometry. However, C, N, and P export fluxes did not increase because A. sanguinea persisted in the water column and did not sink out during the experiment. Accordingly, export fluxes during the study were decou- pled from surface production and sustained by the remain- ing plankton community. Overall, biogeochemical pools and fluxes were surprisingly constant for most of the experiment. We explain this constancy by light limitation through self- shading by phytoplankton and by inorganic nitrogen limita- tion which constrained phytoplankton growth. Thus, gain and loss processes remained balanced and there were few oppor- tunities for blooms, which represents an event where the sys- tem becomes unbalanced. Overall, our mesocosm study re- vealed some key links between ecological and biogeochem- ical processes for one of the most economically important regions in the oceans.
    Keywords: Binary Object; Binary Object (File Size); Binary Object (Media Type); Climate - Biogeochemistry Interactions in the Tropical Ocean; KOSMOS_2017; KOSMOS_2017_Peru; KOSMOS Peru; MESO; Mesocosm experiment; SFB754
    Type: Dataset
    Format: text/tab-separated-values, 11 data points
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  • 2
    Publication Date: 2013-09-23
    Description: Background: Propionibacteria are part of the human microbiota. Many studies have addressed the predominant colonizer of sebaceous follicles of the skin, Propionibacterium acnes, and investigated its association with the skin disorder acne vulgaris, and lately with prostate cancer. Much less is known about two other propionibacterial species frequently found on human tissue sites, Propionibacterium granulosum and Propionibacterium avidum. Here we analyzed two and three genomes of P. granulosum and P. avidum, respectively, and compared them to two genomes of P. acnes; we further highlight differences among the three cutaneous species with proteomic and microscopy approaches. Results: Electron and atomic force microscopy revealed an exopolysaccharide (EPS)-like structure surrounding P. avidum cells, that is absent in P. acnes and P. granulosum. In contrast, P. granulosum possesses pili-like appendices, which was confirmed by surface proteome analysis. The corresponding genes were identified; they are clustered with genes encoding sortases. Both, P. granulosum and P. avidum lack surface or secreted proteins for predicted host-interacting factors of P. acnes, including several CAMP factors, sialidases, dermatan-sulphate adhesins, hyaluronidase and a SH3 domain-containing lipoprotein; accordingly, only P. acnes exhibits neuraminidase and hyaluronidase activities. These functions are encoded on previously unrecognized island-like regions in the genome of P. acnes. Conclusions: Despite their omnipresence on human skin little is known about the role of cutaneous propionibacteria. All three species are associated with a variety of diseases, including postoperative and device-related abscesses and infections. We showed that the three organisms have evolved distinct features to interact with their human host. Whereas P. avidum and P. granulosum produce an EPS-like surface structure and pili-like appendices, respectively, P. acnes possesses a number of unique surface-exposed proteins with host-interacting properties. The different surface properties of the three cutaneous propionibacteria are likely to determine their colonizing ability and pathogenic potential on the skin and at non-skin sites.
    Electronic ISSN: 1471-2164
    Topics: Biology
    Published by BioMed Central
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  • 3
  • 4
    Publication Date: 2013-09-22
    Description: Background Propionibacteria are part of the human microbiota. Many studies have addressed the predominant colonizer of sebaceous follicles of the skin, Propionibacterium acnes, and investigated its association with the skin disorder acne vulgaris, and lately with prostate cancer. Much less is known about two other propionibacterial species frequently found on human tissue sites, Propionibacterium granulosum and Propionibacterium avidum. Here we analyzed two and three genomes of P. granulosum and P. avidum, respectively, and compared them to two genomes of P. acnes; we further highlight differences among the three cutaneous species with proteomic and microscopy approaches. Results Electron and atomic force microscopy revealed an exopolysaccharide (EPS)-like structure surrounding P. avidum cells, that is absent in P. acnes and P. granulosum. In contrast, P. granulosum possesses pili-like appendices, which was confirmed by surface proteome analysis. The corresponding genes were identified; they are clustered with genes encoding sortases. Both, P. granulosum and P. avidum lack surface or secreted proteins for predicted host-interacting factors of P. acnes, including several CAMP factors, sialidases, dermatan-sulphate adhesins, hyaluronidase and a SH3 domain-containing lipoprotein; accordingly, only P. acnes exhibits neuraminidase and hyaluronidase activities. These functions are encoded on previously unrecognized island-like regions in the genome of P. acnes. Conclusions Despite their omnipresence on human skin little is known about the role of cutaneous propionibacteria. All three species are associated with a variety of diseases, including postoperative and device-related abscesses and infections. We showed that the three organisms have evolved distinct features to interact with their human host. Whereas P. avidum and P. granulosum produce an EPS-like surface structure and pili-like appendices, respectively, P. acnes possesses a number of unique surface-exposed proteins with host-interacting properties. The different surface properties of the three cutaneous propionibacteria are likely to determine their colonizing ability and pathogenic potential on the skin and at non-skin sites.
    Electronic ISSN: 1471-2164
    Topics: Biology
    Published by BioMed Central
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  • 5
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    PANGAEA
    In:  Supplement to: Münch, Thomas; Kipfstuhl, Sepp; Freitag, Johannes; Meyer, Hanno; Laepple, Thomas (2017): Constraints on post-depositional isotope modifications in East Antarctic firn from analysing temporal changes of isotope profiles. The Cryosphere, 11(5), 2175-2188, https://doi.org/10.5194/tc-11-2175-2017
    Publication Date: 2023-03-16
    Description: The isotopic composition of water in ice sheets is extensively used to infer past climate changes. In low-accumulation regions their interpretation is however challenged by poorly constrained effects that may influence the initial isotope signal during and after deposition of the snow. This is reflected in snow-pit isotope data from Kohnen Station, Antarctica, which exhibit a seasonal cycle but also strong inter-annual variations that contradict local temperature observations. These inconsistencies persist even after averaging many profiles and are thus not explained by local stratigraphic noise. Previous studies have suggested that post-depositional processes may significantly influence the isotopic composition of East Antarctic firn. Here, we investigate the importance of post-depositional processes within the open-porous firn (〉 10 cm depth) at Kohnen Station by separating spatial from temporal variability. To this end, we analyse 22 isotope profiles obtained from two snow trenches and examine the temporal isotope modifications by comparing the new with published trench data extracted 2 years earlier. The initial isotope profiles undergo changes over time due to downward-advection, firn diffusion and densification in magnitudes consistent with independent estimates. Beyond that, we find further modifications of the original isotope record to be unlikely, or small in magnitude (〈〈 1 per mil RMSD). These results show that the discrepancy between local temperatures and isotopes most likely originates from spatially coherent processes prior to or during deposition, such as precipitation intermittency or systematic isotope modifications acting on drifting or loose surface snow.
    Keywords: AWI_Envi; AWI_Glac; Glaciology @ AWI; Polar Terrestrial Environmental Systems @ AWI
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 6
    Publication Date: 2023-03-16
    Keywords: Age, 14C AMS; Age, dated; Age, dated standard deviation; AWI_Envi; AWI_Perma; AWI Arctic Land Expedition; Comment; Deuterium excess; Event label; Fraction modern carbon; Height above sea level; Laboratory code/label; LATITUDE; LONGITUDE; PERM; Permafrost Research; Polar Terrestrial Environmental Systems @ AWI; RU-Land_2018_Lena_Sobo-Sise; Sample code/label; Sampling permafrost; SOB14-IW3; SOB14-IW4; SOB14-IW5; SOB18-02; SOB18-08; SOB18-09; Sobo-Sise 2018; Sobo-Sise Island; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 3140 data points
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  • 7
    Publication Date: 2023-03-16
    Description: Isotopic measurements of seawater sampled on-board Polarstern research vessel
    Keywords: Arctic; ARK-XXIX/2.1; AWI_Envi; CT; d18O; DATE/TIME; Deuterium excess; ISOARC; Isotope signature of water vapour over the Arctic Ocean; LATITUDE; LONGITUDE; Polarstern; Polar Terrestrial Environmental Systems @ AWI; PS93.1; PS93.1-track; surface water; Underway cruise track measurements; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 57 data points
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  • 8
    Publication Date: 2023-03-16
    Description: Isotopic measurements of seawater sampled on-board Polarstern research vessel
    Keywords: Arctic; ARK-XXIX/2.2; AWI_Envi; CT; d18O; DATE/TIME; Deuterium excess; ISOARC; Isotope signature of water vapour over the Arctic Ocean; LATITUDE; LONGITUDE; Polarstern; Polar Terrestrial Environmental Systems @ AWI; PS93.2; PS93.2-track; surface water; Underway cruise track measurements; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 63 data points
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  • 9
    Publication Date: 2023-03-17
    Description: Isotopic measurements of seawater sampled on-board Polarstern research vessel
    Keywords: ANT-XXXI/1.1; AWI_Envi; CT; d18O; DATE/TIME; Deuterium excess; ISOARC; Isotope signature of water vapour over the Arctic Ocean; LATITUDE; LONGITUDE; Polarstern; Polar Terrestrial Environmental Systems @ AWI; PS95.1; PS95.1-track; surface water; Underway cruise track measurements; water isotopes; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 24 data points
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  • 10
    Publication Date: 2023-03-16
    Description: Isotopic measurements of seawater sampled on-board Polarstern research vessel
    Keywords: ARK-XXIX/3; AWI_Envi; CT; d18O; DATE/TIME; Deuterium excess; ISOARC; Isotope signature of water vapour over the Arctic Ocean; LATITUDE; LONGITUDE; Polarstern; Polar Terrestrial Environmental Systems @ AWI; PS94; PS94-track; surface water; Underway cruise track measurements; δ18O, water; δ Deuterium, water
    Type: Dataset
    Format: text/tab-separated-values, 138 data points
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