Freshwater Picocyanobacteria and their Organic Diet:An Investigation into Organic Nitrogen Assimilation in Freshwater Picocyanobacteria

Freshwater picocyanobacteria are an essential component of our waterbodies, fulfilling a role of global primary producers in waters which are often limited or co-limited by nitrogen. However, they remain relatively poorly understood, especially in comparison to their marine relatives. Also poorly understood is the picocyanobacterial metabolism of organic sources of nitrogen. Researchhas traditionally focused on inorganic sources such as ammonium or nitrate, however it is becoming increasingly evident that organic nitrogen is bioavailable and an integral component of the freshwater nitrogen pool. In this thesis,we sequence five strains of freshwater picocyanobacteria and compare theirencoding capabilities to a common Synechococcus model cyanobacterium (Synechococcus elongatus). We increased the representation of freshwater picocyanobacteria, and found reduced encoding of nitrite-associatedassimilation genes in picocyanobacteria. Further differences in encoded antennae proteins highlight the differences between freshwater picocyanobacteria (Synechococcus spp. of the Syn/Proclade) and Synechococcus elongatus, highlighting the need for a ’true’ freshwater picocyanobacterium model organism. Utilising comparative genomic analyses we investigated the nitrogen assimilation capabilities of freshwater picocyanobacteria, comparing these to picocyanobacteria of different habitatsin addition to larger freshwater cyanobacteria. The diversity displayed among nitrogen assimilation capabilities reveals the evolutionary history of the picocyanobacteria, showcasing the environments in which these organisms evolved. These analyses revealed significant variation in the encoded aminoacid transporters between freshwater picocyanobacteria and larger freshwater cyanobacteria. With different amino acid transporters having different amino acid preferences and uptake rates, this may have implications for amino acid bioavailability. Other sources of potentially differentially bioavailable nitrogen include novel organic forms, such as chitin and glyphosate. Finally, we conduct a growth assay to determine the assimilation capabilities of amino acids as an organic nitrogen source, and explore the proteomic response to growth on selected amino acids using quantitative proteomic analysis. The growth assay revealed widespread amino acid assimilation as a sole nitrogen source for freshwater picocyanobacteria, enabling a wide N pool which may contribute to their limnetic dominance. However, proteomic analysis revealed a subtle stress response in freshwater picocyanobacteria when grown on selected amino acids, potentially due to the accumulation of metabolites. Together, the work increasesour understanding of the nitrogen assimilation capabilities of freshwater picocyanobacteria, with a focus on organic sources of nitrogen

The relationship between regional pain with or without neuropathic symptoms and chronic widespread pain.

This study was performed to test whether the risk of developing chronic widespread pain (CWP) in those with regional pain was augmented in those with symptoms of neuropathic pain (NP). Persons free of CWP completed the Douleur Neuropathique 4 (scores ≥3 indicating NP); demographics; Hospital Anxiety and Depression scale; Pittsburgh Sleep Quality Index; and pain medications. Participants were classified as having no pain, regional pain with no symptoms of NP (NP-), or regional pain with symptoms of NP (NP). At the 12-month follow-up, participants with CWP were identified. Logistic regression estimated the odds ratio, with 95% confidence intervals, of CWP in the NP- and NP groups compared with no pain, and NP compared with NP-. Partial population attributable risks estimated the proportion of CWP attributable to baseline NP- or NP exposure. One thousand one hundred sixty-two participants completed the baseline DN4 and provided pain data at follow-up: 523 (45.0%) had no baseline pain, 562 (48.4%) NP-, and 77 (6.6%) NP. One hundred fifty-three (13.2%) had CWP at 12 months: 19 (3.6%) no pain, 108 (19.2%) NP-, and 26 (33.8%) NP. NP- (2.9 [1.9-4.3]) and NP (2.1 [1.1-4.0]) predicted CWP after adjusting for demographics, Hospital Anxiety and Depression scale, Pittsburgh Sleep Quality Index, and medications. The partial population attributable risk was 41.3% (25.2-54.0) for NP- and 6.0% (0.1-11.6) for NP. The NP group were not more likely to develop CWP when compared directly with NP- (1.5 [0.8-2.8]). Neuropathic pain was relatively rare and predicted a small number of new-onset CWP cases. Using these estimates, treatments targeting NP would at best prevent 6% of CWP cases

Double perovskite cathodes for proton-conducting ceramic fuel cells: are they triple mixed ionic electronic conductors?

Published by National Institute for Materials Science in partnership with Taylor & Francis. 18 O and 2 H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo 2 O 5+δ (PBCO) in flowing air containing 200 mbar of 2 H 2 16 O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity (~1.3 × 10 −11 cm 2 s −1 ) at this temperature and that the presence of water ( 2 H 2 16 O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of ~3. The 2 H distribution, as inferred from the 2 H 2 16 O − SIMS signal, shows an apparent depth profile which could be interpreted as 2 H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials

The interaction of molecular oxygen on LaO terminated surfaces of La2NiO4

Rare-earth metal oxides with perovskite-type crystal structures are under consideration for use as air electrode materials for intermediate to high temperature electrochemical device applications. The surface chemistry of these materials plays a critical role in determining the kinetics of oxygen reduction and exchange reactions. Among various perovskite-structured oxides, certain members of the Ruddlesden–Popper series, e.g. La2NiO4, have been identified as significantly active for surface oxygen interactions. However, the challenge remains to be the identification of the structure and composition of active surfaces, as well as the influence of these factors on the mechanisms of surface exchange reactions. In this contribution, the changes in the electronic structure and the energetics of oxygen interactions on the surfaces of La2NiO4 are analysed using first principles calculations in the Density Functional Theory (DFT) formalism. As for the surface chemistry, LaO termination rather than NiO2 termination is presumed due to recent experimental evidence of the surfaces of various perovskite structured oxides after heat treatment in oxidizing environments being transition metal free. Our findings substantiate the fact that the LaO-terminated surface can indeed participate in the formation of surface superoxo species. Detailed charge transfer analyses revealed that it is possible for such a surface to be catalytically active owing to the enhanced electronic configurations on the neighbouring La sites to surface species. In addition, positively charged oxygen vacancies, relative to the crystal lattice, can act as active sites and catalyse the O–O bond cleavage

Analytical sensitivity of COVID-19 rapid antigen tests: A case for a robust reference standard

Aggressive diagnostic testing remains an indispensable strategy for health and aged care facilities to prevent the transmission of SARS-CoV-2 in vulnerable populations. The preferred diagnostic platform has shifted towards COVID-19 rapid antigen tests (RATs) to identify the most infectious individuals. As such, RATs are being manufactured faster than at any other time in our history yet lack the relevant quantitative analytics required to inform on absolute analytical sensitivity enabling manufacturers to maintain high batch-to-batch reproducibility, and end-users to accurately compare brands for decision making. Here, we describe a novel reference standard to measure and compare the analytical sensitivity of RATs using a recombinant GFP-tagged nucleocapsid protein (NP-GFP). Importantly, we show that the GFP tag does not interfere with NP detection and provides several advantages affording streamlined protein expression and purification in high yields as well as faster, cheaper and more sensitive quality control measures for post-production assessment of protein solubility and stability. Ten commercial COVID-19 RATs were evaluated and ranked using NP-GFP as a reference standard. Analytical sensitivity data of the selected devices as determined with NP-GFP did not correlate with those reported by the manufacturers using the median tissue culture infectious dose (TCID50) assay. Of note, TCID50 discordance has been previously reported. Taken together, our results highlight an urgent need for a reliable reference standard for evaluation and benchmarking of the analytical sensitivity of RAT devices. NP-GFP is a promising candidate as a reference standard that will ensure that RAT performance is accurately communicated to healthcare providers and the public

Orbital Instabilities in a Triaxial Cusp Potential

This paper constructs an analytic form for a triaxial potential that describes the dynamics of a wide variety of astrophysical systems, including the inner portions of dark matter halos, the central regions of galactic bulges, and young embedded star clusters. Specifically, this potential results from a density profile of the form $\rho (m) \propto m^{-1}$, where the radial coordinate is generalized to triaxial form so that $m^2 = x^2/a^2 + y^2/b^2 + z^2/c^2$. Using the resulting analytic form of the potential, and the corresponding force laws, we construct orbit solutions and show that a robust orbit instability exists in these systems. For orbits initially confined to any of the three principal planes, the motion in the perpendicular direction can be unstable. We discuss the range of parameter space for which these orbits are unstable, find the growth rates and saturation levels of the instability, and develop a set of analytic model equations that elucidate the essential physics of the instability mechanism. This orbit instability has a large number of astrophysical implications and applications, including understanding the formation of dark matter halos, the structure of galactic bulges, the survival of tidal streams, and the early evolution of embedded star clusters.Comment: 50 pages, accepted for publication in Ap

Influenza D virus: Serological evidence in the Italian population from 2005 to 2017

Influenza D virus is a novel influenza virus, which was first isolated from an ailing swine in 2011 and later detected in cattle, suggesting that these animals may be a primary natural reservoir. To date, few studies have been performed on human samples and there is no conclusive evidence on the ability of the virus to infect humans. The aim of this serological study was to assess the prevalence of antibodies against influenza D virus in human serum samples collected in Italy from 2005 to 2017. Serum samples were analysed by haemagglutination inhibition and virus neutralization assays. The results showed that the prevalence of antibodies against the virus increased in the human population in Italy from 2005 to 2017, with a trend characterized by a sharp increase in some years, followed by a decline in subsequent years. The virus showed the ability to infect and elicit an immune response in humans. However, prevalence peaks in humans appear to follow epidemics in animals and not to persist in the human population