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result(s) for
"TRACEY, JOHN"
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Microbial N2O consumption in and above marine N2O production hotspots
The ocean is a net source of N
2
O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N
2
O via microbial N
2
O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N
2
O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O
2
tolerance, and community composition of N
2
O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N
2
O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N
2
O cycling. Microbes from the oxic layer consume N
2
O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N
2
O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O
2
and N
2
O gradients right above the ODZ is a previously ignored potential gatekeeper of N
2
O and should be accounted for in the marine N
2
O budget.
Journal Article
Nitrogen and phosphorus differentially control marine biomass production and stoichiometry
Globally averaged, surface particulate nitrogen and phosphorus approximate the 16:1, N:P “Redfield ratio.” In observations, N:P ratios vary latitudinally at ranges attributable to both phytoplankton community composition and physiological acclimation, but their relative contributions to the N:P ratio remain unclear. Here, results from a 29-day mesocosm experiment highlight how inorganic nitrogen and/or phosphorus nutrient supply can affect the bulk particle stoichiometry of a North Pacific Subtropical Gyre plankton community. Nitrogen additions, with and without phosphorus, increase total productivity and diatom abundance, whereas treatments with just phosphorus additions remain similar to the no-nutrient addition control. Continual nitrogen supply without phosphorus results in higher particulate N:P ratios than expected based on the phytoplankton community present. Several P-stress markers identified in those treatments highlight the importance of acclimation in extending particulate N:P ratios beyond the Redfield ratio. Phytoplankton’s ability to maintain growth under P-stress conditions has implications for global carbon cycling.
Mesocosm experiments revealed that both phytoplankton community composition and cellular acclimation influence marine particulate C:N:P ratios, with community shifts more sensitive to nitrogen supply and acclimation to the nutrient N:P supply ratio
Journal Article
All about nitrite: exploring nitrite sources and sinks in the eastern tropical North Pacific oxygen minimum zone
Oxygen minimum zones (OMZs), due to their large volumes of perennially deoxygenated waters, are critical regions for understanding how the interplay between anaerobic and aerobic nitrogen (N) cycling microbial pathways affects the marine N budget. Here, we present a suite of measurements of the most significant OMZ N cycling rates, which all involve nitrite (NO2-) as a product, reactant, or intermediate, in the eastern tropical North Pacific (ETNP) OMZ. These measurements and comparisons to data from previously published OMZ cruises present additional evidence that NO3- reduction is the predominant OMZ N flux, followed by NO2- oxidation back to NO3-. The combined rates of both of these N recycling processes were observed to be much greater (up to nearly 200 times) than the combined rates of the N loss processes of anammox and denitrification, especially in waters near the anoxic–oxic interface. We also show that NO2- oxidation can occur when O2 is maintained near 1 nM by a continuous-purge system, NO2- oxidation and O2 measurements that further strengthen the case for truly anaerobic NO2- oxidation. We also evaluate the possibility that NO2- dismutation provides the oxidative power for anaerobic NO2- oxidation. The partitioning of N loss between anammox and denitrification differed widely from stoichiometric predictions of at most 29 % anammox; in fact, N loss rates at many depths were entirely due to anammox. Our new NO3- reduction, NO2- oxidation, dismutation, and N loss data shed light on many open questions in OMZ N cycling research, especially the possibility of truly anaerobic NO2- oxidation.
Journal Article
The Discovery of Twenty-Eight New Encapsulin Sequences, Including Three in Anammox Bacteria
Many prokaryotes encode protein-based encapsulin nanocompartments, including anaerobic ammonium oxidizing (anammox) bacteria. This study expands the list of known anammox encapsulin systems from freshwater species to include the marine genus
Scalindua
. Two novel systems, identified in “
Candidatus Scalindua rubra
” and “
Candidatus Scalindua
sp. SCAELEC01 167” possess different architectures than previously studied freshwater anammox encapsulins. Characterization of the
S
.
rubra
encapsulin confirms that it can self-assemble to form compartments when heterologously expressed in
Escherichia coli
. BLASTp and HMMER searches of additional genomes and metagenomes spanning a range of environments returned 26 additional novel encapsulins, including a freshwater anammox encapsulin identified in “
Candidatus Brocadia caroliniensis
”. Phylogenetic analysis comparing these 28 new encapsulin sequences and cargo to that of their closest known relatives shows that encapsulins cluster by cargo protein type and therefore likely evolved together. Lastly, prokaryotic encapsulins may be more common and diverse than previously thought. Through searching a small sample size of all public metagenomes and genomes, many new encapsulin systems were unearthed by this study. This suggests that many additional encapsulins likely remain to be discovered.
Journal Article
Improving Transitional Care for Older Adults: Results of a Patient-Centred Quality Improvement Intervention
The objective of this study was to evaluate the implementation and outcomes of a quality improvement intervention for older adults discharged from hospital to home, that used a patient-centred discharge education tool called the Patient-Centered Discharge Plan (PCAP). We conducted a pre–post evaluation of PCAP implementation among patients 65 years and older and discharged home from an acute medical or geriatric admission at two general hospitals. Two patient cohorts, PRE and POST, were analysed using administrative data (n = 3,309) and post-discharge structured interviews in a subset of patients (n = 326). Outcomes were 90-day readmissions and return emergency department (ED) visits, and transition experiences (10-item scale). The PCAP was provided to 20 per cent of 1,683 patients. Transition experience scores increased from PRE to POST at both hospitals (adjusted beta 1.3; 95% CI: 0.8, 1.7), and return ED visits declined in one of the two hospitals (adjusted decline 1.3%; 95% CI: -3.7, 6.2). In conclusion, dedicated resources are needed to support future PCAP implementation.
Journal Article
Clade 2.3.4.4b Highly Pathogenic Avian Influenza H5N1 Pathology in a Common Shorebird Species (Sanderling; Calidris alba) in Virginia, USA
Anseriformes (waterfowl) and Charadriiformes (shorebirds) are well-recognized natural reservoirs of low pathogenic (LP) influenza A viruses (IAVs). Historically, LP IAVs circulate among healthy individuals during seasonal, and often transcontinental, migrations. However, following the introduction of clade 2.3.4.4b highly pathogenic (HP) A/Goose/Guangdong/1/1996 lineage H5 IAV to North America in 2021, countless wild birds succumbed to fatal infections across the Western Hemisphere. Due to their small size and cryptic plumage patterns, opportunities for carcass recovery and postmortem evaluation in sanderlings (Calidris alba) and other shorebirds are rare. A multispecies mortality event in coastal Virginia, USA, in March–April 2024 included sanderlings among other wild bird species. Nine sanderlings underwent postmortem evaluation and clade 2.3.4.4b H5 IAV RNA was detected in pooled oropharyngeal-cloacal swabs from 11/11 individuals by real-time reverse transcription polymerase chain reaction. Histopathology was similar to that in waterfowl and included necrosis in the pancreas and brain and less commonly in the gonad, adrenal gland, spleen, liver, and intestine. Immunohistochemistry revealed IAV antigen labeling in necrotic neurons of the brain (neurotropism) and epithelial cells of the pancreas, gonad, and adrenal gland (epitheliotropism). Describing HP IAV-attributed pathology in shorebirds is key to understanding ecoepidemiology and population health threats in order to further document and compare pathogenesis among avian species.
Journal Article
Piliers d’un modèle d’excellence dans la formation pratique des étudiantes infirmières praticiennes spécialisées en soins de première ligne
Depuis leur introduction en 2007, le gouvernement du Québec a eu pour objectif d’augmenter le nombre d’infirmières praticiennes spécialisées en soins de première ligne (IPSPL) dans le système de santé. L’un des principaux défis à relever pour atteindre cet objectif a été d’assurer la disponibilité de stages cliniques de haute qualité pour la formation des étudiantes IPSPL. Pour relever ce défi, un Centre intégré universitaire de santé et de services sociaux (CIUSSS) s’est associé à une École universitaire de sciences infirmières dans un grand centre urbain pour entreprendre le programme de développement du leadership FORCES d’Excellence en santé Canada. Ce projet, en deux phases, visait à augmenter le nombre de stages de qualité proposés pour la formation des étudiantes IPSPL. Cet article décrit la première phase, qui consistait à élaborer un modèle d’excellence pour la formation clinique des IPSPL. Un cadre de collecte de données a été créé, comprenant une analyse documentaire, des entrevues de groupe et des entrevues individuelles avec divers intervenant(e)s impliqué(e)s dans les stages cliniques. L’analyse thématique a permis d’identifier cinq thèmes clés qui sont devenus les piliers du modèle d’excellence : 1) le partenariat (CIUSSS – Université); 2) la diversité de l’exposition clinique; 3) le soutien et le perfectionnement des superviseures; 4) l’implication des patients à la formation clinique des étudiantes IPSPL; et 5) une culture d’apprentissage fondée sur les forces et les données probantes. Le modèle souligne l’importance du perfectionnement professionnel continu pour les superviseures, en particulier pour la préparation des stages des étudiantes. En ce qui concerne l’expérience de stage, il fait valoir l’importance d’une exposition clinique variée et d’un processus d’accueil et d’intégration dans les milieux de santé pour les étudiantes. Enfin, le modèle met en évidence la nécessité d’assurer une communication claire et efficace entre l’université et le milieu de santé, et de garantir du temps consacré à la supervision clinique.
Journal Article
Three-dimensional solvation structure of ethanol on carbonate minerals
Calcite and magnesite are important mineral constituents of the earth’s crust. In aqueous environments, these carbonates typically expose their most stable cleavage plane, the (10.4) surface. It is known that these surfaces interact with a large variety of organic molecules, which can result in surface restructuring. This process is decisive for the formation of biominerals. With the development of 3D atomic force microscopy (AFM) it is now possible to image solid–liquid interfaces with unprecedented molecular resolution. However, the majority of 3D AFM studies have been focused on the arrangement of water at carbonate surfaces. Here, we present an analysis of the assembly of ethanol – an organic molecule with a single hydroxy group – at the calcite and magnesite (10.4) surfaces by using high-resolution 3D AFM and molecular dynamics (MD) simulations. Within a single AFM data set we are able to resolve both the first laterally ordered solvation layer of ethanol on the calcite surface as well as the following solvation layers that show no lateral order. Our experimental results are in excellent agreement with MD simulations. The qualitative difference in the lateral order can be understood by the differing chemical environment: While the first layer adopts specific binding positions on the ionic carbonate surface, the second layer resides on top of the organic ethyl layer. A comparison of calcite and magnesite reveals a qualitatively similar ethanol arrangement on both carbonates, indicating the general nature of this finding.
Journal Article