scholarly journals Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts

2020 ◽  
Vol 287 (1929) ◽  
pp. 20200620 ◽  
Author(s):  
Charlotte LeKieffre ◽  
Howard J. Spero ◽  
Jennifer S. Fehrenbacher ◽  
Ann D. Russell ◽  
Haojia Ren ◽  
...  
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Planktonic Foraminifera ◽  
Organic Matrix ◽  
Ammonium Assimilation ◽  
Model Calculations ◽  
Transmission Electron ◽  
N Assimilation ◽  
Symbiotic Dinoflagellates ◽  
Enrichment Experiments ◽  
Oligotrophic Ecosystems

The symbiotic planktonic foraminifera Orbulina universa inhabits open ocean oligotrophic ecosystems where dissolved nutrients are scarce and often limit biological productivity. It has previously been proposed that O. universa meets its nitrogen (N) requirements by preying on zooplankton, and that its symbiotic dinoflagellates recycle metabolic ‘waste ammonium’ for their N pool. However, these conclusions were derived from bulk 15 N-enrichment experiments and model calculations, and our understanding of N assimilation and exchange between the foraminifer host cell and its symbiotic dinoflagellates remains poorly constrained. Here, we present data from pulse-chase experiments with 13 C-enriched inorganic carbon, 15 N-nitrate, and 15 N-ammonium, as well as a 13 C- and 15 N- enriched heterotrophic food source, followed by TEM (transmission electron microscopy) coupled to NanoSIMS (nanoscale secondary ion mass spectrometry) isotopic imaging to visualize and quantify C and N assimilation and translocation in the symbiotic system. High levels of 15 N-labelling were observed in the dinoflagellates and in foraminiferal organelles and cytoplasm after incubation with 15 N-ammonium, indicating efficient ammonium assimilation. Only weak 15 N-assimilation was observed after incubation with 15 N-nitrate. Feeding foraminifers with 13 C- and 15 N-labelled food resulted in dinoflagellates that were labelled with 15 N, thereby confirming the transfer of 15 N-compounds from the digestive vacuoles of the foraminifer to the symbiotic dinoflagellates, likely through recycling of ammonium. These observations are important for N isotope-based palaeoceanographic reconstructions, as they show that δ 15 N values recorded in the organic matrix in symbiotic species likely reflect ammonium recycling rather than alternative N sources, such as nitrates.

scholarly journals Heterotrophic Foraminifera Capable of Inorganic Nitrogen Assimilation

2020 ◽  
Vol 11 ◽  
Author(s):  
Clare Bird ◽  
Charlotte LeKieffre ◽  
Thierry Jauffrais ◽  
Anders Meibom ◽  
Emmanuelle Geslin ◽  
...  
Keyword(s):  
Nitrogen Availability ◽  
Secondary Ion Mass Spectrometry ◽  
Inorganic Nitrogen ◽  
Glutamate Synthase ◽  
Ammonium Assimilation ◽  
Biological Productivity ◽  
Benthic Species ◽  
Transmission Electron ◽  
Secondary Ion ◽  
Innate Ability

Nitrogen availability often limits biological productivity in marine systems, where inorganic nitrogen, such as ammonium is assimilated into the food web by bacteria and photoautotrophic eukaryotes. Recently, ammonium assimilation was observed in kleptoplast-containing protists of the phylum foraminifera, possibly via the glutamine synthetase/glutamate synthase (GS/GOGAT) assimilation pathway imported with the kleptoplasts. However, it is not known if the ubiquitous and diverse heterotrophic protists have an innate ability for ammonium assimilation. Using stable isotope incubations (15N-ammonium and 13C-bicarbonate) and combining transmission electron microscopy (TEM) with quantitative nanoscale secondary ion mass spectrometry (NanoSIMS) imaging, we investigated the uptake and assimilation of dissolved inorganic ammonium by two heterotrophic foraminifera; a non-kleptoplastic benthic species, Ammonia sp., and a planktonic species, Globigerina bulloides. These species are heterotrophic and not capable of photosynthesis. Accordingly, they did not assimilate 13C-bicarbonate. However, both species assimilated dissolved 15N-ammonium and incorporated it into organelles of direct importance for ontogenetic growth and development of the cell. These observations demonstrate that at least some heterotrophic protists have an innate cellular mechanism for inorganic ammonium assimilation, highlighting a newly discovered pathway for dissolved inorganic nitrogen (DIN) assimilation within the marine microbial loop.

A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre

1992 ◽  
Vol 50 (2) ◽  
pp. 1024-1025
Author(s):  
Jun Liu ◽  
Katie E. Gunnison ◽  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Mechanical Properties ◽  
Ion Beam ◽  
Laminated Composite ◽  
Organic Matrix ◽  
Pearl Oyster ◽  
Interfacial Structure ◽  
Interfacial Region ◽  
Thin Sections ◽  
Organic Layers ◽  
Transmission Electron

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.

Effects of Concurrent Co or Ti Silicidation on Transient Diffusion and End-of-Range Damage in Phosphorus Implanted Silicon

1992 ◽  
Vol 262 ◽  
Author(s):  
J.W. Honeycutt ◽  
J. Ravi ◽  
G. A. Rozgonyi
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Complete Removal ◽  
Dislocation Loops ◽  
Enhanced Diffusion ◽  
Depth Profiles ◽  
Enhanced Dissolution ◽  
Implantation Damage ◽  
Transmission Electron ◽  
Defect Behavior ◽  
Secondary Ion

ABSTRACTThe effects of Ti and Co silicidation on P+ ion implantation damage in Si have been investigated. After silicidation of unannealed 40 keV, 2×1015 cm-2 P+ implanted junctions by rapid thermal annealing at 900°C for 10–300 seconds, secondary ion mass spectrometry depth profiles of phosphorus in suicided and non-silicided junctions were compared. While non-silicided and TiSi2 suicided junctions exhibited equal amounts of transient enhanced diffusion behavior, the junction depths under COSi2 were significantly shallower. End-of-range interstitial dislocation loops in the same suicided and non-silicided junctions were studied by planview transmission electron microscopy. The loops were found to be stable after 900°C, 5 minute annealing in non-silicided material, and their formation was only slightly effected by TiSi2 or COSi2 silicidation. However, enhanced dissolution of the loops was observed under both TiSi2 and COSi2, with essentially complete removal of the defects under COSi2 after 5 minutes at 900°C. The observed diffusion and defect behavior strongly suggest that implantation damage induced excess interstitial concentrations are significantly reduced by the formation and presence of COSi2, and to a lesser extent by TiSi2. The observed time-dependent defect removal under the suicide films suggests that vacancy injection and/or interstitial absorption by the suicide film continues long after the suicide chemical reaction is complete.

Effect of Laser Thermal Processing on Defect Evolution in Silicon

2002 ◽  
Vol 717 ◽  
Author(s):  
Erik Kuryliw ◽  
Kevin S. Jones ◽  
David Sing ◽  
Michael J. Rendon ◽  
Somit Talwar
Keyword(s):  
Point Defects ◽  
Thermal Processing ◽  
Defect Formation ◽  
Secondary Ion Mass Spectrometry ◽  
Laser Energy ◽  
Process Window ◽  
Loop Formation ◽  
Transmission Electron ◽  
Ultra Shallow Junctions ◽  
Laser Thermal Processing

AbstractLaser Thermal Processing (LTP) involves laser melting of an implantation induced preamorphized layer to form highly doped ultra shallow junctions in silicon. In theory, a large number of interstitials remain in the end of range (EOR) just below the laser-formed junction. There is also the possibility of quenching in point defects during the liquid phase epitaxial regrowth of the melt region. Since post processing anneals are inevitable, it is necessary to understand both the behavior of these interstitials and the nature of point defects in the recrystallized-melt region since they can directly affect deactivation and enhanced diffusion. In this study, an amorphizing 15 keV 1 x 1015/cm2 Si+ implant was done followed by a 1 keV 1 x 1014/cm2 B+ implant. The surface was then laser melted at energy densities between 0.74 and 0.9 J/cm2 using a 308 nm excimer-laser. It was found that laser energy densities above 0.81 J/cm2 melted past the amorphous-crystalline interface. Post-LTP furnace anneals were performed at 750°C for 2 and 4 hours. Transmission electron microscopy was used to analyze the defect formation after LTP and following furnace anneals. Secondary ion mass spectrometry measured the initial and final boron profiles. It was observed that increasing the laser energy density led to increased dislocation loop formation and increased diffusion after the furnace anneal. A maximum loop density and diffusion was observed at the end of the process window, suggesting a correlation between the crystallization defects and the interstitial evolution.

scholarly journals Subcellular Investigation of Photosynthesis-Driven Carbon Assimilation in the Symbiotic Reef Coral Pocillopora damicornis

mBio ◽  
2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Christophe Kopp ◽  
Isabelle Domart-Coulon ◽  
Stephane Escrig ◽  
Bruno M. Humbel ◽  
Michel Hignette ◽  
...  
Keyword(s):  
Lipid Droplets ◽  
Secondary Ion Mass Spectrometry ◽  
Reef Coral ◽  
Carbon Assimilation ◽  
Isotopic Labeling ◽  
Cellular Level ◽  
Coral Tissue ◽  
Pocillopora Damicornis ◽  
Carbon And Nitrogen ◽  
Transmission Electron

ABSTRACT  Reef-building corals form essential, mutualistic endosymbiotic associations with photosynthetic Symbiodinium dinoflagellates, providing their animal host partner with photosynthetically derived nutrients that allow the coral to thrive in oligotrophic waters. However, little is known about the dynamics of these nutritional interactions at the (sub)cellular level. Here, we visualize with submicrometer spatial resolution the carbon and nitrogen fluxes in the intact coral-dinoflagellate association from the reef coral Pocillopora damicornis by combining nanoscale secondary ion mass spectrometry (NanoSIMS) and transmission electron microscopy with pulse-chase isotopic labeling using [13C]bicarbonate and [15N]nitrate. This allows us to observe that (i) through light-driven photosynthesis, dinoflagellates rapidly assimilate inorganic bicarbonate and nitrate, temporarily storing carbon within lipid droplets and starch granules for remobilization in nighttime, along with carbon and nitrogen incorporation into other subcellular compartments for dinoflagellate growth and maintenance, (ii) carbon-containing photosynthates are translocated to all four coral tissue layers, where they accumulate after only 15 min in coral lipid droplets from the oral gastroderm and within 6 h in glycogen granules from the oral epiderm, and (iii) the translocation of nitrogen-containing photosynthates is delayed by 3 h. IMPORTANCE  Our results provide detailed in situ subcellular visualization of the fate of photosynthesis-derived carbon and nitrogen in the coral-dinoflagellate endosymbiosis. We directly demonstrate that lipid droplets and glycogen granules in the coral tissue are sinks for translocated carbon photosynthates by dinoflagellates and confirm their key role in the trophic interactions within the coral-dinoflagellate association.

Substantially Transparent Pt, Pd, Rh, And Re Films: Preparation and Properties

1987 ◽  
Vol 111 ◽  
Author(s):  
D. E. Aspnes ◽  
A. Heller
Keyword(s):  
Light Transmission ◽  
Building Blocks ◽  
Poor Quality ◽  
Model Calculations ◽  
Transmission Electron ◽  
Metal Volume ◽  
Potential Applications ◽  
Metallic Catalyst ◽  
Anomalous Transparency ◽  
Best Fit

AbstractFilms of Pt, Pd, Rh, and Re with metal volume fractions of 0.3 to 0.5 have been prepared by mass-transport-limited photoelectrodeposition onto (001) p-InP photocathodes from ∼5 × 10−5 M solutions of the metal ions in 1 M HClO4. These films exhibit their normal catalytic activities (e.g., in hydrogen evolution) and have normal crystal structures, yet are substantially more transparent than equivalent dense films of the same metal loading per unit area. Effective-medium analysis of the spectroellipsometrically measured dielectric functions of these films shows that the anomalous transparency is due to microstructure: depolarization factors and metal packing fractions obtained by best-fit model calculations indicate dendritic (Rh), particulate (Pt, Pd), or platelet (Re) forms that are poorly interconnected in directions parallel to the surface, and whose dimensions are all small compared to the wavelength of light. Transmission electron micrographs confirm these results and reveal that these films consist of primary building blocks of ca. 5 nm crystallites that are organized into relatively loosely packed secondary structures. Potential applications of these films include the formation of efficient metallic-catalyst-coated photoelectrodes on poor-quality semiconductors.

Pulsed Laser Melting of Amorphous Silicon: Time-Resolved and Post-Irradiation Studies

1983 ◽  
Vol 23 ◽  
Author(s):  
D. H. Lowndes ◽  
R. F. Wood ◽  
C. W. White ◽  
J. Narayan
Keyword(s):  
Pulsed Laser ◽  
Threshold Value ◽  
Dynamical Response ◽  
Cross Sectional ◽  
Time Resolved ◽  
Model Calculations ◽  
Fine Grained ◽  
Transmission Electron ◽  
Incident Laser Pulse ◽  
Thermal Melting

ABSTRACTMeasurements of the time of the onset of melting of self-implantation amorphized (a) Si, during an incident laser pulse, have been combined with modified melting model calculations and measurements of surface melt duration to demonstrate that the thermal conductivity, Ka, of a-Si is very low (≃0.02 W/cm-K). Ka is also shown to be the dominant parameter determining the dynamical response of ionimplanted Si to pulsed laser radiation; the latent heat and melting temperature of a-Si are relatively unimportant. Cross-sectional transmission electron micrographs on implantation-amorphized Si layers of several different thicknesses show that for energy densities less than the threshold value for complete annealing there are usually two distinct regions in the re-solidified a-Si, consisting of fine-grained and large-grained polycrystalline Si, respectively. The presence of the fine-grained poly-Si suggests that bulk nucleation occurs directly from the highly undercooled liquid phase. Thermal melting model calculations suggest that the nucleation temperature, Tn is ≃1200°C.

scholarly journals A Microbial Nitrogen Engine Modulated by Bacteriosyncytia in Hexactinellid Sponges: Ecological Implications for Deep-Sea Communities

2021 ◽  
Vol 8 ◽  
Author(s):  
Manuel Maldonado ◽  
María López-Acosta ◽  
Kathrin Busch ◽  
Beate M. Slaby ◽  
Kristina Bayer ◽  
...  
Keyword(s):  
Deep Sea ◽  
Functional Integration ◽  
Ammonium Assimilation ◽  
Ammonium Nitrogen ◽  
Low Oxygen ◽  
Microbial Nitrogen ◽  
Transmission Electron ◽  
Oxygen Conditions ◽  
Aerobic And Anaerobic ◽  
Hexactinellid Sponges

Hexactinellid sponges are common in the deep sea, but their functional integration into those ecosystems remains poorly understood. The phylogenetically related species Schaudinnia rosea and Vazella pourtalesii were herein incubated for nitrogen and phosphorous, returning markedly different nutrient fluxes. Transmission electron microscopy (TEM) revealed S. rosea to host a low abundance of extracellular microbes, while Vazella pourtalesii showed higher microbial abundance and hosted most microbes within bacteriosyncytia, a novel feature for Hexactinellida. Amplicon sequences of the microbiome corroborated large between-species differences, also between the sponges and the seawater of their habitats. Metagenome-assembled genome of the V. pourtalesii microbiota revealed genes coding for enzymes operating in nitrification, denitrification, dissimilatory nitrate reduction to ammonium, nitrogen fixation, and ammonia/ammonium assimilation. In the nitrification and denitrification pathways some enzymes were missing, but alternative bridging routes allow the microbiota to close a N cycle in the holobiont. Interconnections between aerobic and anaerobic pathways may facilitate the sponges to withstand the low-oxygen conditions of deep-sea habitats. Importantly, various N pathways coupled to generate ammonium, which, through assimilation, fosters the growth of the sponge microbiota. TEM showed that the farmed microbiota is digested by the sponge cells, becoming an internal food source. This microbial farming demands more ammonium that can be provided internally by the host sponges and some 2.6 million kg of ammonium from the seawater become annually consumed by the aggregations of V. pourtalesii. Such ammonium removal is likely impairing the development of the free-living bacterioplankton and the survival chances of other sponge species that feed on bacterioplankton. Such nutritional competitive exclusion would favor the monospecific character of the V. pourtalesii aggregations. These aggregations also affect the surrounding environment through an annual release of 27.3 million kg of nitrite and, in smaller quantities, of nitrate and phosphate. The complex metabolic integration among the microbiota and the sponge suggests that the holobiont depends critically on the correct functioning of its N-driven microbial engine. The metabolic intertwining is so delicate that it changed after moving the sponges out of their habitat for a few days, a serious warning on the conservation needs of these sponge aggregations.

scholarly journals Изменение структуры и свойств приповерхностного слоя Si, имплантированного Zn, в зависимости от флюенса облучения ионами -=SUP=-132-=/SUP=-Xe-=SUP=-26+-=/SUP=- с энергией 167 МэВ

2019 ◽  
Vol 53 (3) ◽  
pp. 332
Author(s):  
В.В. Привезенцев ◽  
В.С. Куликаускас ◽  
В.А. Скуратов ◽  
О.С. Зилова ◽  
А.А. Бурмистров ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Zinc Oxide ◽  
Cross Section ◽  
Secondary Ion Mass Spectrometry ◽  
Sample Surface ◽  
Transmission Electron ◽  
Oxide Phases ◽  
Secondary Ion ◽  
Surface Pores ◽  
Scanning Electron

AbstractSingle-crystal n -Si(100) wafers are implanted with ^64Zn^+ ions with an energy of 50 keV and dose of 5 × 10^16 cm^–2. Then the samples are irradiated with ^132Xe^26+ ions with an energy of 167 MeV in the range of fluences from 1 × 10^12 to 5 × 10^14 cm^–2. The surface and cross section of the samples are visualized by scanning electron microscopy and transmission electron microscopy. The distribution of implanted Zn atoms is studied by time-of-flight secondary-ion mass spectrometry. After irradiation with Xe, surface pores and clusters consisting of a Zn–ZnO mixture are observed at the sample surface. In the amorphized subsurface Si layer, zinc and zinc-oxide phases are detected. After irradiation with Xe with a fluence of 5 × 10^14 cm^–2, no zinc or zinc-oxide clusters are detected in the samples by the methods used in the study.

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