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Roman salt production in the <i>civitas Menapiorum</i>. A study of the implemented technological process on the salt production sites through the analysis of the briquetage from the region Zeebrugge-Dudzele
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Molecular adaptation to high pressure in cytochrome P450 1A and aryl hydrocarbon receptor systems of the deep-sea fish <i>Coryphaenoides armatus</i>
No full textLimited knowledge of the molecular evolution of deep-sea fish proteomes so far suggests that a few widespread residue substitutions in cytosolic proteins binding hydrophilic ligands contribute to resistance to the effects of high hydrostatic pressure (HP). Structure-function studies with additional protein systems, including membrane bound proteins, are essential to provide a more general picture of adaptation in these extremophiles. We explored molecular features of HP adaptation in proteins binding hydrophobic ligands, either in lipid bilayers (cytochrome P450 1A - CYP1A) or in the cytosol (the aryl hydrocarbon receptor - AHR), and their partners P450 oxidoreductase (POR) and AHR nuclear translocator (ARNT), respectively. Cloning studies identified the full-length coding sequence of AHR, CYP1A and POR, and a partial sequence of ARNT from Coryphaenoides armatus, an abyssal gadiform fish thriving down to 5000 m depth. Inferred protein sequences were aligned with many non-deep-sea homologs to identify unique amino acid substitutions of possible relevance in HP adaptation. Positionally unique substitutions of various physicochemical properties were found in all four proteins, usually at sites of strong-to-absolute residue conservation. Some were in domains deemed important for protein-protein interaction or ligand binding. In addition, some involved removal or addition of beta-branched residues; local modifications of beta-branched residue patterns could be important to HP adaptation. In silico predictions further suggested that some unique substitutions might substantially modulate the flexibility of the polypeptide segment in which they are found. Repetitive motifs unique to the abyssal fish AHR were predicted to be rich in glycosylation sites, suggesting that post-translational changes could be involved in adaptation as well. Recombinant CYP1A and AHR showed functional properties (spectral characteristics, catalytic activity and ligand binding) that demonstrate proper folding at 1 atm, indicating that they could be used as deep-sea fish protein models to further evaluate protein function under pressure. This article is part of a Special Issue entitled: Cytochrome P450 biodiversity and biotechnology, edited by Erika Plettner, Gianfranco Gilardi, Luet Wong, Vlada Urlacher, Jared Goldstone"
Drowned landscapes of the Belgian Continental Shelf: implications for northwest European landscape evolution and preservation potential for submerged heritage = Verdronken landschappen van het Belgisch deel van de Noordzee: implicaties voor noordwest Europese landschapsontwikkeling en bewaringspotentieel van onderwater erfgoed
No full textThe Belgian Continental Shelf is the smallest exclusive economic zone of the North Sea and is bounded by the French, British and Dutch Continental Shelves, however the number of economic and societal claims is very large, comprising fishing, military defence, sand extraction, maintenance dredging, shipping, wind farms, pipelines and cables. On top of that, the scarce economic resource of the Quaternary sediments of the Belgian Continental Shelf is thin and fragmented, which is the main reason why it has been so difficult up to now to produce a coherent reconstruction of the Quaternary evolution of the BCS. Moreover, the limited thickness of the Quaternary cover makes its entire section potentially vulnerable to the economic claims. Marine spatial planning hence exists to accommodate these various economic interests. It is a process to allocate the space available on sea to certain actors within a certain time frame and at the same time to ensure that all ecological, economic and social objectives are achieved. An ecosystem vision and involvement of all stakeholders (science, industry, policy) are hereby of great importance. Within the Marine Spatial Plan of 2014 it is recognised that next to shipwrecks all traces of human presence, be it cultural, historic or archaeological, belong to the submerged heritage. However, the marine spatial plan does not elucidate on how this submerged heritage is to be protected from damage or destruction that comes forth from these economic claims. Furthermore, it does not elaborate on palaeontological bone material, which is inherently connected to past human activities and use of the land and is therefore a fundamental part of this submerged heritage (from here on, submerged heritage refers to drowned palaeolandscapes, prehistorich archaeology and palaeontological bone material). An efficient policy at sea is therefore imperative. A first step to achieve a more efficient policy was developed by the SeArch project (2013–2016). The project offered solutions to improve the offshore policy by: 1) providing stakeholders with new and improved remote sensing technologies and an efficient survey methodology for the assessment of submerged heritage; 2) to provide stakeholders with a new, sustainable management framework regarding submerged heritage, and including marine spatial planning; 3) to provide practical guidance for the stakeholders on how to implement the new methodology and management approach. The one thing that remains underrepresented to provide the necessary tools for an efficient offshore policy is a thorough overview of the Quaternary stratigraphy of the BCS and what geological formation processes lie at its base. This is a pivotal step to understand why and viii where submerged heritage may be preserved within the Quaternary deposits, i.e. the preservation potential
Biochemodynamic features of metal ions bound by micro- and nano-plastics in aquatic media
Get PDFA simple model, based on spherical geometry, is applied to the description of release kinetics of metal species from nano- and micro-plastic particles. Compiled literature data show that the effective diffusion coefficients, Deff, for metal species within plastic polymer bodies are many orders of magnitude lower than those applicable for metal ions in bulk aqueous media. Consequently, diffusion of metal ions in the aqueous medium is much faster than that within the body of the plastic particle. So long as the rate of dissociation of any inner-sphere metal complexes is greater than the rate of diffusion within the particle body, the latter process is the limiting step in the overall release kinetics of metal species that are sorbed within the body of the plastic particle. Metal ions that are sorbed at the very particle/medium interface and/or associated with surface-sorbed ligands do not need to traverse the particle body and thus in the diffusion-limiting case, their rate of release will correspond to the rate of diffusion in the aqueous medium. Irrespective of the intraparticulate metal speciation, for a given diffusion coefficient, the proportion of metal species released from plastic particles within a given time frame increases dramatically as the size of the particle decreases. The ensuing consequences for the chemodynamics and bioavailability of metal species associated with plastic micro- and nano-particles in aquatic systems are discussed and illustrated with practical examples
The cell envelope structure of cable bacteria
Get PDFCable bacteria are long, multicellular micro-organisms that are capable of transporting electrons from cell to cell along the longitudinal axis of their centimeter-long filaments. The conductive structures that mediate this long-distance electron transport are thought to be located in the cell envelope. Therefore, this study examines in detail the architecture of the cell envelope of cable bacterium filaments by combining different sample preparation methods (chemical fixation, resin-embedding, and cryo-fixation) with a portfolio of imaging techniques (scanning electron microscopy, transmission electron microscopy and tomography, focused ion beam scanning electron microscopy, and atomic force microscopy). We systematically imaged intact filaments with varying diameters. In addition, we investigated the periplasmic fiber sheath that remains after the cytoplasm and membranes were removed by chemical extraction. Based on these investigations, we present a quantitative structural model of a cable bacterium. Cable bacteria build their cell envelope by a parallel concatenation of ridge compartments that have a standard size. Larger diameter filaments simply incorporate more parallel ridge compartments. Each ridge compartment contains a similar to 50 nm diameter fiber in the periplasmic space. These fibers are continuous across cell-to-cell junctions, which display a conspicuous cartwheel structure that is likely made by invaginations of the outer cell membrane around the periplasmic fibers. The continuity of the periplasmic fibers across cells makes them a prime candidate for the sought-after electron conducting structure in cable bacteria
Seasonal mass variations show timing and magnitude of meltwater storage in the Greenland Ice Sheet
Get PDFThe Greenland Ice Sheet (GrIS) is currently losing ice mass. In order to accurately predict future sea level rise, the mechanisms driving the observed mass loss must be better understood. Here, we combine data from the satellite gravimetry mission Gravity Recovery and Climate Experiment (GRACE), surface mass balance (SMB) output of the Regional Atmospheric Climate Model v. 2 (RACMO2), and ice discharge estimates to analyze the mass budget of Greenland at various temporal and spatial scales. We find that the mean rate of mass variations in Greenland observed by GRACE was between −277 and −269 Gt yr−1 in 2003–2012. This estimate is consistent with the sum (i.e., −304±126 Gt yr−1) of individual contributions – surface mass balance (SMB, 216±122 Gt yr−1) and ice discharge (520±31 Gt yr−1) – and with previous studies. We further identify a seasonal mass anomaly throughout the GRACE record that peaks in July at 80–120 Gt and which we interpret to be due to a combination of englacial and subglacial water storage generated by summer surface melting. The robustness of this estimate is demonstrated by using both different GRACE-based solutions and different meltwater runoff estimates (namely, RACMO2.3, SNOWPACK, and MAR3.9). Meltwater storage in the ice sheet occurs primarily due to storage in the high-accumulation regions of the southeast and northwest parts of Greenland. Analysis of seasonal variations in outlet glacier discharge shows that the contribution of ice discharge to the observed signal is minor (at the level of only a few gigatonnes) and does not explain the seasonal differences between the total mass and SMB signals. With the improved quantification of meltwater storage at the seasonal scale, we highlight its importance for understanding glacio-hydrological processes and their contributions to the ice sheet mass variability