47242 research outputs found
Sort by
A third type of PETase from the marine Halopseudomonas lineage
No full textThe enzymatic degradation of polyethylene terephthalate (PET) offers a sustainable solution for PET recycling. Over the past two decades, more than 100 PETases have been characterized, primarily exhibiting similar sequences and structures. Here, we report PET-degrading α/β hydrolases, including HaloPETase1 from the marine Halopseudomonas lineage, thereby extending the narrow sequence space by novel features at the active site. The crystal structure of HaloPETase1 was determined to a resolution of 1.16 Å, revealing a unique active site architecture and a lack of the canonical π-stacking clamp found in PETases so far. Further, variations in active site composition and loop structures were observed. Additionally, we found five more enzymes from the same lineage, two of which have a high similarity to type IIa bacterial PETases, while the other three resemble HaloPETase1. All these enzymes exhibited high salt tolerance ranging from 2.5 to 5 M NaCl, leading to higher total product releases upon PET degradation at 40 or 50°C. Based on these findings, we propose an extension of the existing PETase classification system to include type III PETases
DNA Metabarcoding as a Tool to Study Plankton Responses to Warming and Salinity Change in Mesocosms
No full textClimate change is transforming marine ecosystems, with rising temperatures and changing salinity patterns expected to reshape plankton communities in the Baltic Sea. As key components of marine food webs and biogeochemical cycles, plankton are highly sensitive to environmental change. Here, we examined the effects of warming and salinity change on plankton communities using a mesocosm experiment at the Tvärminne Zoological Station, Finland. We employed both traditional microscopy-based identification and DNA metabarcoding (18S rRNA and COI markers) to assess shifts in phytoplankton, ciliates and mesozooplankton. Our findings indicate that salinity primarily affected higher trophic levels, while warming influenced lower ones. Warmer conditions increased community evenness and favoured mixotrophic and heterotrophic taxa, whereas salinity effects were most pronounced in rotifers and copepods, reflecting species-specific tolerances. Interactive effects varied, with salinity sometimes buffering warming impacts and other times intensifying them, highlighting complex stressor interactions. Microscopy allowed for a more precise quantification of plankton abundance, whereas metabarcoding captured a broader taxonomic diversity. Our results suggest that, within the tested salinity range (3–10.5 PSU), higher salinities supported a more classical marine food web structure, characterised by larger and more complex zooplankton such as copepods. In contrast, freshening and warming conditions were associated with shifts towards smaller, mixotrophic and bloom-forming plankton taxa, with potential consequences for ecosystem functioning. This study highlights metabarcoding's value in mesocosm research while emphasising the need to refine molecular techniques for ecological interpretations
Volcanic crisis reveals coupled magma system at Santorini and Kolumbo
No full textVolcanic crises, driven by renewed magma inflow and migration, result in surface deformation and seismicity that can provide unique insights into the structure of volcanic systems and magmatic processes. Although the highly explosive volcanoes of Santorini and Kolumbo 1,2 in the Greek Aegean Sea are just 7 km apart, their potentially coupled deep magmatic feeding systems are only poorly understood 3,4 . The 2025 volcano–tectonic crisis of Santorini simultaneously affected both volcanic centres, providing insights into a complex, multistorage feeder system. Here we integrate onshore and marine seismological data with geodetic measurements to reconstruct magma migration before and during the crisis. Gradual inflation in the Santorini caldera, beginning in mid-2024, preceded the January 2025 intrusion of a magma-filled dike sourced from a mid-crustal reservoir beneath Kolumbo, indicating a link between the two volcanoes. Joint inversion of ground and satellite-based deformation data indicates that approximately 0.31 km 3 of magma intruded as an approximately 13-km-long dike, reactivating principal regional faults and arresting 3–5 km below the seafloor. The 2024–2025 resurgence of magmatic activity beneath both volcanic centres and their apparent coupling provides insights into the dynamic interplay of magma storage, transport and reservoir failure beneath neighbouring volcanoes
Beyond supergenes: the diverse roles of inversions in trait evolution
No full textHighlights:
Recent genome-wide studies show that most chromosomal inversions in eukaryotic genomes are small, often spanning only a few hundred base pairs.
Research has predominantly focused on large, supergene-like inversions, limiting our understanding of inversions that are smaller or contribute to continuous traits, whose functional and evolutionary roles – particularly in influencing continuous traits and eco-evolutionary dynamics – remain poorly understood.
The length of an inversion affects the number of genes and genetic elements it captures, influencing functional effects, genome reorganisation, and the likelihood of an inversion containing co-adapted gene complexes.
Improving our understanding of the role of inversions in trait evolution will require the study of small inversions, coupled with experimental assays and functional annotation to go beyond observational data and clarify their role in ecoevolutionary dynamics.
Chromosomal inversions are ubiquitous across the Tree of Life, with genome-wide studies revealing a bias toward smaller inversions, yet research has disproportionately focused on large, supergene-like inversions linked to discrete phenotypes. This limits our understanding of inversions' roles in trait evolution, as their size affects their potential functional impact. Investigation of smaller inversions and multi-inversion genotypes is crucial to elucidate their role in shaping continuous traits and evolutionary adaptation. Addressing this requires a shift towards a systematic study of smaller inversions and the use of experimental assays and functional annotation to identify the evolutionary forces driving different genomic trait architectures
Metabologenomics and chemometrics to unlock the biosynthetic potential of marine actinobacteria from Antarctica
No full text
Monitoring the Danish Straits using acoustic telemetry to understand how environmental drivers influence fish migrations in a major swimway
No full textImpact of Different Types of Meltwater Runoff on Pelagic and Benthic Processes in Young Sound, NE Greenland
No full textGlacial retreat due to climate warming alters the pathway through which meltwater enters Arctic fjords. In the Tyrolerfjord–Young Sound system (NE Greenland), meltwater is delivered by two contrasting rivers: the Tyroler River, which flows directly from the glacier into the fjord, and the Zackenberg River, which passes through a proglacial lake. We investigated the impact of these different glacial sources on the pelagic system and fjord sediment biogeochemistry, with a focus on carbon and iron cycling. We quantified particulate organic carbon and particulate organic nitrogen, as well as δ 13 C and δ 15 N of the organic matter in the suspended and sinking fractions in the water column. In sediment, we quantified total organic carbon (TOC) and total nitrogen, δ 13 C and δ 15 N of the organic matter, porewater concentrations of Fe, Mn, and different fractions of solid‐phase Fe, O 2 microprofiles and sulfate reduction rates. We find that the passage through a proglacial lake decreases the impact of the glacier on the fjord, as the lake acts as a trap for glacial material, decreasing sediment input to the fjord system. In the fjord sediments, a stronger redox‐cycling of iron was found further away from the rivers, which is mainly driven by the higher TOC content. Overall, our data suggest that, with glacial retreat, the impact of glaciers on the marine and the benthic systems in fjords will become weaker, and reduce long‐term carbon sequestration in Arctic fjord sediments.
Plain Language Summary
Glaciers crush, grind, and leach the bedrock they are overriding, and meltwater transport dissolved compounds and fine material downstream toward the coast. With ongoing warming, glaciers retreat further onto land, causing the glacial meltwater to flow over land for longer distances before it drains into the fjord. In some cases, lakes will form, which catch sediment and increase water temperature and residence time, potentially changing what meltwater brings into the fjord. The Tyrolerfjord‐Young Sound system is influenced by different meltwater sources, of which one river only flows over land for a short distance, while the other passes through a proglacial lake and flows over land for a longer distance. Our results show that a proglacial lake can catch a high proportion of the particulate material in the meltwater. As a consequence, the marine system tends to receive less terrestrial input, only with a highly pulsed input, often once a year. In the fjord sediment, we find that the balance between glacial‐ and marine input controls the pathways through which organic matter gets respired. Our data also show that with glacial retreat and the formation of proglacial lakes, the potential for carbon burial in fjord sediments will most likely decrease.
Key Points
A proglacial lake functions as an efficient sediment trap, reducing the downstream impact of glacial meltwater on the fjord ecosystem
The balance of sedimentary Mn, Fe and SO 4 2− reduction changes along the fjord axis and leads to intense Fe‐cycling further out in the fjord
High vertical flux of carbon to the seafloor and low oxygen consumption indicate efficient burial of terrestrial carbon in sediment
Linking microbial community composition, microbial biomass and extracellular polymeric substances to organic matter lability gradients in sediments of the tidal Elbe River
No full textHighlights
• Organic matter availability is key driver shaping microbial community composition.
• More labile carbon reduces bacterial but fosters archaeal diversity and vice versa.
• Archaea dominate terminal carbon release in spite of low relative abundances (<1 %).
• Microbial taxon richness to biomass ratio is an indicator for carbon lability.
• EPS composition reflects carbon lability and metabolic activity gradients.
Abstract
The port of Hamburg represents a transition zone between upstream, shallow regions of high net primary production and downstream deep and more turbulent waters in the tidal Elbe River in northwestern Germany. Correspondingly, strong gradients of degradable organic matter (OM) on a distance of a few river kilometers had been identified. This study links microbial community composition using 16S metagenomic amplicons and extracellular polymeric substances (EPS) composition to the observed gradients of sediment OM lability. It was hypothesized that lability gradients caused by higher concentrations of biogenic, autochthonous OM upstream and greater share of already stabilized OM downstream reflect in gradients of microbial community composition, diversity and EPS characteristics.
Indeed, available OM was found to act as key driver regulating syntrophic microbial community composition and associated metabolic features, with location-specific overriding the effect of seasonal variations. Upstream sites with high available OM featuring lower bacterial but increased archaeal diversity and elevated methane and carbon dioxide fluxes, whereas lower OM lability downstream fostered a more diverse bacterial but decreased archaeal diversity. The ratio between microbial taxon richness and biomass correlated inversely with OM transformation rates. These patterns also reflected in increased EPS concentration produced in response to metabolic needs (i.e. polysaccharides and proteins), whereas structural components such as lipids, which can be more resistant under the prevailing anoxic conditions, remained more evenly distributed along the transect. Although bacterial relative abundances exceeded archaeal abundances (<1 %) by far, archaeal functional significance remained pivotal for the final release of carbon as methane and carbon dioxide under the mostly reducing conditions in the deposited sediment