Investigations on the cuticle of the polychaete elytra using energy dispersive X-ray analysis

Energy dispersive X-ray analysis of elements with Z>11 in a SEM (scanning electron microscope) was used to investigate the elytra ofLagisca extenuata, Lepidonotus clava, andHarmothoe areolata from Naples (Italy) and Banyuls (France). High concentrations of halogens and a few other elements were found in certain papillae in samples from both locations. Additional TEM-examinations and X-ray analysis of thin sections revealed that the halogen concentration is inversely related to the collagen content of the matrix. The halogens are presumably bound to tyrosines, which occur in these structures. In addition, accumulation of Mn²⁺ and possibly Fe³⁺ in the papillae might depend on environmental conditions. The results show that valuable information about the chemical composition of biological structures can be obtained by energy dispersive X-ray analysis. Moreover, the results indicate that this method may be useful for environmental investigations.This work is part of a doctoral thesis, written at the Zoological Institute of the University at Hamburg.     

Localization of selenium in bacterial cells using TEM and energy dispersive X-ray analysis

Bacteria isolated from lake sediment samples reduced sodium selenite to elemental selenium. Finestructural observations were made on a number of different bacterial species cultured in the presence of sodium selenite. Examination of Escherichia coli and a Pseudomonas species revealed electron-dense deposits of irregular shape, composed of smaller units, within the cytoplasm but not on the cell wall and cell membrane. Cells of Aeromonas and Flavobacterium species exhibited conspicuous intranuclear fibrillary aggregates and different electron-dense inclusions. It appeared that the membrane structures were somewhat more easily stained in some bacterial cells after growth on agar plates containing sodium selenite. The deposits and fibrillary accumulations were interpreted to contain selenium on the basis of energy dispersive X-ray analysis. Control preparations and cells grown in the presence of sodium selenate were void of any fine-structural abnormalities. Alterations in fine structure are discussed in relation to the metabolism of selenium by bacterial cells and possible sites of inhibition.Abbreviations TEM transmission electron microscopy - EDX energy dispersive X-ray     

Elemental analysis of particles in fungal zoospores

The elemental composition of gamma particles in zoospores ofAllomyces macrogynus andBlastocladiella emersonii was determined by use of energy dispersive X-ray analysis of glutaraldehyde fixed, thin section zoospores. Isolated preparations of gamma particles were also examined. Gamma particles contained no detectable elements. Similar sized, globular, electron dense cytoplasmic inclusions contained phosphorus and calcium. We suggest that previous studies assigning calcium and phosphorus to gamma particles may have been based on confusion of these two types of cytoplasmic inclusions.     

The use of X-ray microanalysis to demonstrate the uptake of the molluscicide copper sulphate by slug eggs

Summary Copper has been localized in copper sulphate treated eggs of the slug Agriolimax reticulatus (Mü). This has been accomplished using a freeze-fracture technique, the freeze-dried halves of the fractured eggs being analysed in the scanning electron microscope, using both energy dispersive and wavelength dispersive X-ray microanalysis systems. The distribution of copper obtained using these methods has been compared with that achieved using a standard histochemical technique. Both techniques revealed that the copper is initially retained in the perivitelline membranes. The application of X-ray microanalysis to such studies is discussed.This research was supported by the Agricultural Research Council (G.B.), Grant No. AG 72/13     

POTASSIUM IN POLYPHOSPHATE BODIES OF CHLORELLA PYRENOIDOSA (CHLOROPHYCEAE) AS DETERMINED BY X-RAY MICROANALYSIS1

Potassium is an important component information of polyphosphate bodies (PB) by Chlorella pyrenoidosa Chick. However, it was not detected in PB by X-ray energy dispersive microanalyses when the specimens were subjected to a standard preparation procedure for transmission electron microscopy. Intact cells were incinerated at 350 C on stainless steel grids coated with silicon monoxide. X-ray spectra from PB showed conspicuous peaks of energy counts in the Kα lines for phosphorus and potassium. It is proposed that potassium is a major cationic component of PB in C. pyrenoidosa grown in potassium sufficient medium.     

A study of methods for in situ X-ray energy dispersive analysis of polyphosphate bodies in Plectonema boryanum

A variety of preparative methods for in situ X-ray energy dispersive analysis were tested to determine their effects on the elemental composition of polyphosphate bodies in P. boryanum. The bodies were found to contain large amounts of P and K and small amounts of Ca and Mg. Air drying, freeze-drying and freeze-drying from a liquid nitrogen slush all gave similar results. Fixation of the cells in glutaraldehyde and/or OsO₄ resulted in loss of the K and enhancement of the Ca peak. Magnesium was lost during embedding in epoxy.     

Localization of cadmium in the root cells of <Emphasis Type="Italic">Allium cepa</Emphasis> by energy dispersive x-ray analysis

Allium cepa L. roots were exposed to 0.1 and 1.0 mM Cd for 6, 24 and 48 h and the localization of Cd in the root tissue was investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) were performed on frozen-dried tissues of roots. No Cd was detected in the roots treated with only 0.1 mM Cd, while after exposure to higher Cd concentration (1.0 mM) Cd was observed in cell wall and in cytoplasm in the epidermis, cortex and vascular tissues in the roots.     

Manganese in the shell of Centropyxis (Rhizopodea: Protozoa)

Summary The proteinaceous shells of Centropyxis hirsuta contain a relatively high concentration of manganese in an amorphous state. The concentrations of manganese fill the alveoli which are characteristic of the shell structure. Observations based on cultured animals and subsequently examined by X-ray diffraction, a solid state energy dispersive X-ray analyser, and an analytical electron microscope, lead to the conclusions that manganese is selectively absorbed by Centropyxis hirsuta and deposited in the shell.     

Synthesis and study of physico-chemical properties of a new chiral Schiff base ligand and its metal complex

A new chiral amino acid Schiff base ligand (Salarg) and its metal complex (Mn-Salarg) have been synthesized using l-Arginine, a naturally occurring chiral diamine with two kinds of asymmetric α-, ε-NH₂ groups. This new Salarg-ligand and Mn-Salarg complex are characterized with the help of ultraviolet, fluorescence and infrared spectroscopy. Their crystal systems are determined by X-ray powder diffraction method. The elemental analysis has been carried out by energy dispersive X-ray analysis (EDAX). The presence and percentage of metal in the complex have been detected and estimated by energy dispersive X-ray fluorescence (EDXRF) spectroscopy. Circular dichroism spectroscopy has revealed the chiral nature of the Salarg-ligand and its metal complex. Furthermore, a comparative study of this new chiral Salarg-ligand and its complex has been made with the well known achiral Salen ligand and its metal complex (Mn-Salen).     

Energy-dispersive X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes

Klebsiella aerogenes forms electron-dense partieles on the cell surface in response to the presence of cadmium ions in the growth medium. These particles ranged from 20 to 200 nm in size, and quantitative energy dispersive X-ray analysis established that they comprise cadmium and sulfur in a 1:1 ratio. This observation leads to the conclusion that the particles are cadmium sulfide crystallites. A combination of atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and acid-labile sulfide analysis revealed that the total intracellular and bound extracellular cadmium:sulfur ratio is also 1:1, which suggests that the bulk of the cadmium is fixed as extracellular cadmium sulfide. The tolerance of K. acrogenes to cadmium ions and the formation of the cadmium sulfide crystallites were dependent on the buffer composition of the growth medium. The addition of cadmium ions to phosphate-buffered media resulted in cadmium phosphate precipitates that remove the potentially toxic cadmium ions from the growth medium. Electrondense particles formed on the surfaces of bacteria grown under these conditions were a combination of cadmium sulfide and cadmium phosphates. The specific bacterial growth rate in the exponential phase of batch cultures was not affected by up to 2mM cadmium in Tricine-buffered medium, but formation of cadmium sulfide crystallites was maximal during the stationary phase of batch culture. Cadmium tolerance was much lower (10 to 150 M) in growth media buffered with Tris, Bistris propane, Bes, Tes, or Hepes. These results illustrate the importance of considering medium composition when comparing levels of bacterial cadmium tolerance.Abbreviations EDXA Energy dispersive X-ray analysis - AAS Atomic absorption spectroscopy - TEM Transmission electron microscopy - SEM Scanning electron microscopy - ICP-MS Inductively coupled plasma mass spectrometry - ALSA Acid-labile sulfide analysis     

Isolation of a strain of <Emphasis Type="Italic">Acidithiobacillus caldus</Emphasis> and its role in bioleaching of chalcopyrite

A moderately thermophilic and acidophilic sulfur-oxidizing bacterium named S₂, was isolated from coal heap drainage. The bacterium was motile, Gram-negative, rod-shaped, measured 0.4 to 0.6 by 1 to 2 μm, and grew optimally at 42–45°C and an initial pH of 2.5. The strain S₂ grew autotrophically by using elemental sulfur, sodium thiosulfate and potassium tetrathionate as energy sources. The strain did not use organic matter and inorganic minerals including ferrous sulfate, pyrite and chalcopyrite as energy sources. The morphological, biochemical, physiological characterization and analysis based on 16S rRNA gene sequence indicated that the strain S₂ is most closely related to Acidithiobacillus caldus (>99% similarity in gene sequence). The combination of the strain S₂ with Leptospirillum ferriphilum or Acidithiobacillus ferrooxidans in chalcopyrite bioleaching improved the copper-leaching efficiency. Scanning electron microscope (SEM) analysis revealed that the chalcopyrite surface in a mixed culture of Leptospirillum ferriphilum and Acidithiobacillus caldus was heavily etched. The energy dispersive X-ray (EDX) analysis indicated that Acidithiobacillus caldus has the potential role to enhance the recovery of copper from chalcopyrite by oxidizing the sulfur formed during the bioleaching progress.     

Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction.Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of > 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm.Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed.     

Isolation and Characterization of Exopolysaccharide Secreted by a Toxic Dinoflagellate, <Emphasis Type="Italic">Amphidinium carterae</Emphasis> Hulburt 1957 and Its Probable Role in Harmful Algal Blooms (HABs)

Extracellular polymeric substances (EPS) produced by a toxic dinoflagellate Amphidinium carterae Hulburt 1957 was isolated and characterized. Molecular masses of the EPS were about 233 and 1,354 kDa. Spectral analyses by ¹H nuclear magnetic resonance and Fourier Transformed–Infrared Spectroscopy revealed the characteristic of the functional groups viz. primary amine, carboxyl, halide, and sulfate groups present in the EPS. However, five elements (C, O, Na, S, and Ca) were detected by scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDX) analysis. X-ray diffraction and differential scanning calorimetric analysis confirmed the amorphous nature of EPS, which was comprised of an average particle size of 13.969 μm (d 0.5) with 181 nm average roughness. Two monosaccharide constituents, galactose (73.13%) and glucose (26.87%) were detected by gas chromatography–mass spectroscopy analysis. Thermal gravimetric analysis revealed that degradation of EPS obtained from A. carterae takes place in three steps. The EPS produced by A. carterae was found to be beneficial for the growth of both A. carterae and Bacillus pumilus. The potential heterogeneous properties of EPS may play an important role in harmful algal bloom.     

Solute sorting in grass leaves: the transpiration stream

Solutes distribute differentially between leaf tissues and cells. The present study tested the hypothesis that certain solutes are supplied preferentially to the epidermis in the transpiration stream, by-passing mesophyll cells along bundle sheath extensions. Using energy dispersive X-ray analysis of extracted cell sap, the distribution of solutes was studied in the emerged zone (transpiring) and the elongation zone (non-transpiring) of the developing leaf three of barley (Hordeum vulgare L.). The basic distribution of Cl, K, P and Ca between epidermis and bulk tissue, and between cells within the epidermis, was similar in the two leaf regions. However, in the emerged zone differences in solute concentrations between tissues and cells were greater. A local reduction in transpiration rate along the emerged portion of the blade specifically prevented Ca from accumulating to high levels in epidermal cells close to stomata. It is concluded that differences in solute concentrations between epidermal cells and other leaf tissues can be established in the absence of transpiration, but that they require transpiration for their full expression. Peristomatal transpiration appears to be responsible for high Ca in interstomatal cells.Abbreviations EDX-analysis Energy-dispersive X-ray analysis - IS-cell Interstomatal cell - R-cell Ridge cell - TR-cell Trough cell     

Biological Synthesis of Semiconductor Zinc Sulfide Nanoparticles by Immobilized Rhodobacter sphaeroides

A novel, clean biological transformation reaction by immobilized Rhodobacter sphaeroides has been developed for the synthesis of zinc sulfide (ZnS) nanoparticles with an average diameter of 8 nm. The nanoparticles were examined by X-ray diffraction, transmission electron microscopy, energy dispersive analyses of X-rays, UV–vis optical absorption and photoluminescence spectra. The average diameter of ZnS nanoparticles varied according to the culture time.     

The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor

The corrosion behaviour of galvanized steel in cooling tower water containing a biocide and a corrosion inhibitor was investigated over a 10-month period in a hotel. Planktonic and sessile numbers of sulphate reducing bacteria (SRB) and heterotrophic bacteria were monitored. The corrosion rate was determined by the weight loss method. The corrosion products were analyzed by energy dispersive X-ray spectroscopy and X-ray diffraction. A mineralized, heterogeneous biofilm was observed on the coupons. Although a biocide and a corrosion inhibitor were regularly added to the cooling water, the results showed that microorganisms, such as SRB in the mixed species biofilm, caused corrosion of galvanized steel. It was observed that Zn layers on the test coupons were completely depleted after 3?months. The Fe concentrations in the biofilm showed significant correlations with the weight loss and carbohydrate concentration (respectively, p?<?0.01 and p?<?0.01).     

Polyphosphate granules in encysted zoospores of Rozella allomycis

Methods of ultracytochemistry and of X-ray energy dispersive analysis have been used to demonstrate that the gamma-like granules in encysted zoospores of the chytrid Rozella allomycis contain polyphosphate. The possibility that cysts contain two classes of polyphosphate granules which differ in structure, in function, and in origin is discussed.     

Investigation of Elemental Sulfur Speciation Transformation Mediated by Acidithiobacillus ferrooxidans

The speciation transformation of elemental sulfur mediated by the leaching bacterium Acidithiobacillus ferrooxidans was investigated using an integrated approach including scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, and X-ray absorption near edge spectroscopy (XANES). Our results showed that when grown on elemental sulfur powder, At. ferrooxidans ATCC23270 cells were first attached to sulfur particles and modified the surface sulfur with some amphiphilic compounds. In addition, part of the elemental sulfur powder might be converted to polysulfides. Furthermore, sulfur globules were accumulated inside the cells. XANES spectra of these cells suggested that these globules consisted of elemental sulfur bound to thiol groups of protein. Huan He and Cheng-Gui Zhang made equal contributions to this paper.     

Community structure and function in a H2-based membrane biofilm reactor capable of bioreduction of selenate and chromate

Two different H₂-based, denitrifying membrane-biofilm reactors (MBfRs) initially reduced Se(VI) or Cr(VI) stably to Se⁰ or Cr(III). When the oxidized contaminants in the influent were switched, each new oxidized contaminant was reduced immediately, and its reduction soon was approximately the same or greater than it had been in its original MBfR. The precipitation of reduced selenium and chromium in the biofilm was verified by scanning electron microscopy and energy dispersive X-ray analysis. These results on selenate and chromate reduction are consistent with the interpretation that the H₂-based biofilm community had a high level of functional diversity. The communities’ structures were assessed by cloning analysis. Dechloromonas spp., a known perchlorate-reducing bacteria, dominated the clones from both reactors during selenate and chromate reductions, which suggests that it may have functional diversity capable of reducing selenate and chromate as secondary and dissimilatory acceptors.     

Mechanical and Chemical Characterization of a TiC/C System Synthesized Using a Focus Plasma Arc

Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting elemental powders using self-propagating high-temperature synthesis technique in an ultra-high plasma inert medium in a single stage. The TiC was exposed to a high-temperature inert medium to allow recrystallization. The product was then characterized using field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Rietveld refinement, nanoindentation, and micro-hardness to determine the product’s properties. The recorded micro-hardness of the product was 3660 HV, which is a 14% enhancement and makes is comparable to TiC materials.