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The sponge-like biomineralized calcite materials found in echinoderm skeletons are of interest in terms of both structure formation and biological function. Despite their crystalline atomic structure, they exhibit curved interfaces that have been related to known triply periodic minimal surfaces. Here, we investigate the endoskeleton of the sea urchin Cidaris rugosa that has long been known to form a microstructure related to the Primitive surface. Using X-ray tomography, we find that the endoskeleton is organized as a composite material consisting of domains of bicontinuous microstructures with different structural properties. We describe, for the first time, the co-occurrence of ordered single Primitive and single Diamond structures and of a disordered structure within a single skeletal plate. We show that these structures can be distinguished by structural properties including solid volume fraction, trabeculae width and, to a lesser extent, interface area and mean curvature. In doing so, we present a robust method that extracts interface areas and curvature integrals from voxelized datasets using the Steiner polynomial for parallel body volumes. We discuss these very large-scale bicontinuous structures in the context of their function, formation and evolution.

Introduction: Biological N2 fixation in feather-mosses is one of the largest inputs of new nitrogen (N) to boreal forest ecosystems; however, revealing the fate of newly fixed N within the bryosphere (i.e. bryophytes and their associated organisms) remains uncertain. Methods: Herein, we combined 15N tracers, high resolution secondary ion mass-spectrometry (NanoSIMS) and a molecular survey of bacterial, fungal and diazotrophic communities, to determine the origin and transfer pathways of newly fixed N2 within feather-moss (Pleurozium schreberi) and its associated microbiome. Results: NanoSIMS images reveal that newly fixed N2, derived from cyanobacteria, is incorporated into moss tissues and associated bacteria, fungi and micro-algae. Discussion: These images demonstrate that previous assumptions that newly fixed N2 is sequestered into moss tissue and only released by decomposition are not correct. We provide the first empirical evidence of new pathways for N2 fixed in feather-mosses to enter the boreal forest ecosystem (i.e. through its microbiome) and discuss the implications for wider ecosystem function.

Introduction: Biological N2 fixation in feather-mosses is one of the largest inputs of new nitrogen (N) to boreal forest ecosystems; however, revealing the fate of newly fixed N within the bryosphere (i.e. bryophytes and their associated organisms) remains uncertain., Methods: Herein, we combined 15N tracers, high resolution secondary ion mass-spectrometry (NanoSIMS) and a molecular survey of bacterial, fungal and diazotrophic communities, to determine the origin and transfer pathways of newly fixed N2 within feather-moss (Pleurozium schreberi) and its associated microbiome., Results: NanoSIMS images reveal that newly fixed N2, derived from cyanobacteria, is incorporated into moss tissues and associated bacteria, fungi and micro-algae., Discussion: These images demonstrate that previous assumptions that newly fixed N2 is sequestered into moss tissue and only released by decomposition are not correct. We provide the first empirical evidence of new pathways for N2 fixed in feather-mosses to enter the boreal forest ecosystem (i.e. through its microbiome) and discuss the implications for wider ecosystem function.

Poly(2-hydroxyethyl methacrylate) hydrogels incorporating copper nanoparticles (Cu-PHEMA) were prepared by a two-step process. In the first step, porous PHEMA hydrogels containing aqueous Cu(II) were formed by photo-induced phase separation polymerization in aqueous formulations containing 2-hydroxyethyl methacrylate (HEMA), a photoinitator, a cross-linker, and CuSO4. In the second step, the Cu(II) ions were reduced to Cu(0) (Cu NPs) by hydrazine. The Cu-PHEMA hydrogels were red-brown due to the presence of the Cu NPs, and X-ray diffraction studies confirmed the NPs were crystalline Cu and not CuO. The porous PHEMA and Cu-PHEMA hydrogels exhibited the polymer droplet morphology characteristic of sponges formed by induced phase separation polymerization of HEMA in water. The Cu NPs were stable inside the hydrogel, and leaching of Cu NPs into water was very slow. Leached Cu NPs moderately inhibited the growth of Escherichia coli or Staphylococcus aureus bacteria in the surrounding medium. Incorporation of Cu NPs inside PHEMA hydrogels did not change compression strength of hydrogels. Graphical abstract

Poly(2-hydroxyethyl methacrylate) hydrogels doped with gold nanoparticles (Au-PHEMA) were prepared via photochemically and thermally induced phase separation polymerization of aqueous formulations containing 2-hydroxyethyl methacrylate (HEMA), a cross-linker, an initiator, and either KAuCl4 or (CH3)2SAuCl. In photopolymerizations, 2,2-dimethoxy-2-phenylacetophenone (DPAP) served as the photoinitiator of polymerization of HEMA but also appeared to play a role in the reduction of Au(III) to Au(0). For thermal polymerizations, potassium persulfate (K2S2O8) was used to initiate polymerization of HEMA, and it appeared that the resulting PHEMA was responsible for the reduction of Au(III) to Au(0). The Au-PHEMA hydrogels exhibited the morphology based on a network of polymer droplets and interconnected pores characteristic of PHEMA formed via polymerization-induced phase separation, with only minor differences in the sizes of the polymer droplets and mechanical properties. The application of Au-PHEMA as a platform for surface-enhanced Raman scattering was demonstrated using an 80 ppb solution of 4-ethynylbenzaldehyde as an analyte.

To better understand the physiology and acclimation capability of the cell, one of the great challenges of the future is to access the interior of a cell and unveil its chemical landscape (composition and distribution of elements and molecules). Chemical imaging has greatly improved in sensitivity and spatial resolution to visualize and quantify nutrients, metabolites, toxic elements, and drugs in single cells at the subcellular level. This review aims to present the current potential of these emerging imaging technologies and to guide biologists towards a strategy for interrogating biological processes at the nanoscale. We also describe various solutions to combine multiple imaging techniques in a correlative way and provide perspectives and future directions for integrative subcellular imaging across different disciplines.

Poly(2-hydroxyethyl methacrylate) sponges doped with silver nanoparticles (Ag NP-PHEMA) were prepared by irradiation of aqueous solutions containing 2-hydroxyethyl methacrylate (HEMA) and silver nitrate in the presence of a cross-linking agent and a photoinitiator. The Ag NP-PHEMA sponges had polymer droplet morphology with interconnected pores, characteristic of PHEMA sponges prepared by polymerization-induced phase separation. The Ag NP-PHEMA sponges were yellow-brown, whereas PHEMA sponges were white. For formation of Ag NP-PHEMA, the size of the polymer droplets was larger and the rate of polymerization was increased compared to PHEMA sponges formed under similar conditions but in the absence of silver nitrate. Mechanical strength, as indicated by compression testing, was similar for Ag NP-PHEMA and PHEMA sponges. Nanoparticles slowly leached out of Ag NP-PHEMA sponges, exerting antibacterial activity against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. Notably, Ag NPs that leached were nontoxic to human corneal epithelial (HCE-T) cells.

In contrast to the situation in plants inhabiting most of the world’s ecosystems, mycorrhizal fungi are usually absent from roots of the only two native vascular plant species of maritime Antarctica, Deschampsia antarctica and Colobanthus quitensis. Instead, a range of ascomycete fungi, termed dark septate endophytes (DSEs), frequently colonise the roots of these plant species. We demonstrate that colonisation of Antarctic vascular plants by DSEs facilitates not only the acquisition of organic nitrogen as early protein breakdown products, but also as non‐proteinaceous d‐amino acids and their short peptides, accumulated in slowly‐decomposing organic matter, such as moss peat. Our findings suggest that, in a warming maritime Antarctic, this symbiosis has a key role in accelerating the replacement of formerly dominant moss communities by vascular plants, and in increasing the rate at which ancient carbon stores laid down as moss peat over centuries or millennia are returned to the atmosphere as CO2.