Characterization of hollow glass microspheres with potential for regional climate intervention to preserve snow and ice surfaces

Cold regions including the Arctic are warming fast, resulting in increased losses of snow and ice cover. A climate intervention approach, where hollow glass microspheres (HGMs) are applied on snow and ice surfaces such as Artic sea ice has been suggested for ice preservation. HGMs are commercial materials, typically in the 10–200 μm diameter size range. They are very lightweight, highly reflective materials with a high crush strength. It is suggested that through that reflectivity, their application onto snow and ice surfaces can increase the albedo, and thus stabilize snow and ice covers, for example aid the formation of multiyear sea ice. In this study we tested the stability and behaviour of different HGMs under stress conditions to gain knowledge on their potential environmental fate. Stability tests, measured as maintenance of positive buoyancy, during sediment interaction, repeated freezing and thawing and prolonged exposure in seawater showed differences in environmental stability of the tested materials with stability depending on wall thickness and surface integrity. None of the tested materials seemed to be very susceptible to biofouling under the conditions tested. However, leaching of elements, especially Si was observed for some materials, potentially indicating dissolution of the HGMs in seawater over time. Further studies are needed to determine the element dissolution from HGMs and other potential environmental implications such as impacts on organisms. Although this paper is directed towards using HGMs in a local climate intervention application the findings may be of general interest for other uses of HGM materials.publishedVersio

Dual-polarized chipless humidity sensor tag

In this letter, a miniaturized, flexible and high data dense dual-polarized chipless radio frequency identification (RFID) tag is presented. The tag is designed within a minuscule footprint of 29 × 29 mm2 and has the ability to encode 38-bit data. The tag is analyzed for flexible substrates including Kapton® HN DuPont™ and HP photopaper. The humidity sensing phenomenon is demonstrated by mapping the tag design, using silver nano-particle based conductive ink on HP photopaper substrate. It is observed that with the increasing moisture, the humidity sensing behavior is exhibited in RF range of 4.1–17.76 GHz. The low-cost, bendable and directly printable humidity sensor tag can be deployed in a number of intelligent tracking applications

The regulatory landscape of plastic governance - a Norwegian perspective

In this report we co-produced a matrix of governance fragmentation in the Norwegian plastic value chain to assess where there are overlaps, interplay and synergies to be aligned. This also included an assessment of the global level of plastic regulatory fragmentation as it relates to the upcoming negotiations for a global treaty to end plastic pollution.Norges forskningsrådpublishedVersio

Synthesis of hemes found in heme-copper oxidases of Bacillus subtilis

The last step of aerobic respiration, the reduction of dioxygen to water, is catalysed by terminal oxidases. These oxidases can be divided into two unrelated families, the heme-copper oxidases and the cytochrome bd-type oxidases. These enzymes contain two or more heme molecules as prosthetic groups. Heme is an iron-containing ring-closed tetrapyrrole. All eukaryotic and most bacterial oxidases belong to the heme-copper superfamily. The Gram-positive bacterium Bacillus subtilis can synthesise two heme-copper oxidases; cytochrome caa3 and cytochrome aa3. Both these oxidases contain two heme A molecules. The cytochrome caa3 also contain one heme C. Heme B (protoheme IX) is the last common precursor for the synthesis of both heme A and heme C. Heme C is formed by covalent attachment of protoheme IX to a cysteine-containing motif -CXXCH- in the apocytochrome c polypeptide. This attachment occurs on the outside of the cytoplasmic membrane in bacteria and requires transport of heme B across the membrane. The ccmABCDEFGH genes are necessary for heme C synthesis in Escherichia coli. CcmABC consitutes a putative ABC-type transport system proposed to transport heme out of the cell. Using E. coli mutant strains and a periplasmic heme-reporter system it was shown that CcmA and CcmC are not required for transport of heme B to the periplasm. CcdA is a membrane protein required for cytochrome c syntheis in Bacillus subtilis. It was demonstrated that CcdA-deficient cells are blocked in heme C synthesis at some step after heme and apocytochrome have been exported across the cytoplasmic membrane. Heme A is synthesised from heme B with heme O as an intermediate. Two polytopic membrane proteins, encoded by the ctaA and ctaB genes, are essential for heme A synthesis in B. subtilis. CtaB catalyses the conversion of heme B to heme O. A ctaB paralogue, ctaO, has been found in B. subtilis. The CtaO protein is not required for heme O synthesis, but seems to have heme O synthase activity. CtaA functions in the conversion of heme O to heme A and is known to bind heme B and heme A. A system for easy and rapid purification of B. subtilis CtaA has been worked out. The transmembrane topology of CtaA has been determined. Four histidine residues, which are invariant in CtaA from different organisms, have been mutagenised. Analysis of the isolated mutant proteins demonstrates that CtaA can bind heme O and provides information on properties of the enzyme

The Bacillus subtilis ctaB paralogue, yjdK, can complement the heme A synthesis deficiency of a CtaB-deficient mutant

Heme A is a prosthetic group in many respiratory oxidases. It is synthesised from heme B (protoheme IX) with heme O as an intermediate. In Bacillus subtilis two genes required for heme A synthesis, ctaA and ctaB, have been identified. CtaB is the heme O synthase and CtaA is involved in the conversion of heme O to heme A. A ctaB paralogue, yjdK, has been identified through the B. subtilis genome sequencing project. In this study we show that when carried on a low copy number plasmid, the yjdK gene can complement a ctaB deletion mutant with respect to heme A synthesis. Our results indicate that YjdK has heme O synthase activity. We therefore suggest that yjdK be renamed as ctaO

Heme A Synthase Enzyme Functions Dissected by Mutagenesis of Bacillus subtilis CtaA

Heme A, as a prosthetic group, is found exclusively in respiratory oxidases of mitochondria and aerobic bacteria. Bacillus subtilis CtaA and other heme A synthases catalyze the conversion of a methyl side group on heme O into a formyl group. The catalytic mechanism of heme A synthase is not understood, and little is known about the composition and structure of the enzyme. In this work, we have: (i) constructed a ctaA deletion mutant and a system for overproduction of mutant variants of the CtaA protein in B. subtilis, (ii) developed anaffinity purification procedure for isolation of preparative amounts of CtaA, and (iii) investigated the functional roles of four invariant histidine residues in heme A synthase by in vivo and in vitro analyses of the properties of mutant variants of CtaA. Our results show an important function of three histidine residues for heme A synthase activity. Several of the purified mutant enzyme proteins contained tightly bound heme O. One variant also contained trapped hydroxylated heme O, which is a postulated enzyme reaction intermediate. The findings indicate functional roles for the invariant histidine residues and provide strong evidence that the heme A synthase enzyme reaction includes two consecutive monooxygenations

Escherichia coli ccm in-frame mutants can produce periplasmic cytochrome b but not cytochrome c

Escherichia coli CcmA, CcmB and CcmC polypeptides are required for cytochrome c synthesis and are thought to constitute the subunits of an ABC-type transporter as judged from sequence data, Using a periplasmic reporter system based on Bacillus subtilis cytochrome c-550 and E. coli cytochrome b-562 we show that the synthesis of the b-type cytochrome in the periplasm is normal in E, coli ccmA and ccmC in-frame deletion mutants, Mutants deleted for ccmF or ccmG encoding a component of a putative cytochrome c-heme lyase and a membrane bound thioredoxin-like protein, respectively, have the same phenotype, The ccm mutants produce cytochrome c-550 polypeptide, but not holocytochrome c, Taken together the results demonstrate that heme can be transported to the periplasm by a ccm-independent mechanism. (C) 1997 Federation of European Biochemical Societies

Microbial communities related to biodegradation of dispersed Macondo oil at low seawater temperature with Norwegian coastal seawater

The Deepwater Horizon (DWH) accident in 2010 created a deepwater plume of small oil droplets from a deepwater well in the Mississippi Canyon lease block 252 (‘Macondo oil’). A novel laboratory system was used in the current study to investigate biodegradation of Macondo oil dispersions (10 μm or 30 μm median droplet sizes) at low oil concentrations (2 mg l−1) in coastal Norwegian seawater at a temperature of 4–5°C. Whole metagenome analyses showed that oil biodegradation was associated with the successive increased abundances of Gammaproteobacteria, while Alphaproteobacteria (Pelagibacter) became dominant at the end of the experiment. Colwellia and Oceanospirillales were related to n-alkane biodegradation, while particularly Cycloclasticus and Marinobacter were associated with degradation of aromatic hydrocarbons (HCs). The larger oil droplet dispersions resulted in delayed sequential changes of Oceanospirillales and Cycloclasticus, related with slower degradation of alkanes and aromatic HCs. The bacterial successions associated with oil biodegradation showed both similarities and differences when compared with the results from DWH field samples and laboratory studies performed with deepwater from the Gulf of Mexico

Microbial communities related to biodegradation of dispersed Macondo oil at low seawater temperature with Norwegian coastal seawater

The Deepwater Horizon (DWH) accident in 2010 created a deepwater plume of small oil droplets from a deepwater well in the Mississippi Canyon lease block 252 (‘Macondo oil’). A novel laboratory system was used in the current study to investigate biodegradation of Macondo oil dispersions (10 μm or 30 μm median droplet sizes) at low oil concentrations (2 mg l−1) in coastal Norwegian seawater at a temperature of 4–5°C. Whole metagenome analyses showed that oil biodegradation was associated with the successive increased abundances of Gammaproteobacteria, while Alphaproteobacteria (Pelagibacter) became dominant at the end of the experiment. Colwellia and Oceanospirillales were related to n-alkane biodegradation, while particularly Cycloclasticus and Marinobacter were associated with degradation of aromatic hydrocarbons (HCs). The larger oil droplet dispersions resulted in delayed sequential changes of Oceanospirillales and Cycloclasticus, related with slower degradation of alkanes and aromatic HCs. The bacterial successions associated with oil biodegradation showed both similarities and differences when compared with the results from DWH field samples and laboratory studies performed with deepwater from the Gulf of Mexico.Microbial communities related to biodegradation of dispersed Macondo oil at low seawater temperature with Norwegian coastal seawaterpublishedVersio