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A description is given of results from developing a new lithium-loaded plastic scintillator based on a styrene–methacrylic acid copolymer. Measurements of the light output and transparency of samples of the new material allow the optimum concentrations of the scintillation additive, wave shifter, secondary solvent, and lithium-containing additive to be determined.

The fabrication of ZrO2 nanostructures, such as nanowires or nanorods, arrayed on substrates and having certain and reproducible microstructures and chemical compositions presents a challenge. Here we synthesize, for the first time, 1- and 3-dimensional zirconium-oxide nanostructures highly aligned on substrates via the self-organized anodizing and subsequent re-anodizing of pure Zr (99.99%) layers, following the initial formation of a porous anodic alumina (PAA) overlayer, at voltages ranging 50 to 500 V. The films formed after the dissolution of PAA consist of upright-standing zirconium-oxide nano-protrusions shaped like ‘polyps’ (anodized samples) or pillars and rods (re-anodized samples) anchored by tiny widespread nanoroots to the bottom oxide layer. The arrays synthesized in 0.2 M H3PO4, which was chosen as a model electrolyte, consist of stoichiometric ZrO2, the suboxides Zr2O3 and ZrO, a minor amount of Al2O3, and traces of PO43− species. Unexpectedly, all the anodic zirconium oxide in the re-anodized sample forms in an amorphous and perfectly flawless manner. The oxide grows due to the cross-migration of oxygen and zirconium ions with nearly equal transport numbers, which is a unique situation for anodic films on pure Zr metal. Annealing the films at 600 °C in air increases the oxidation state of the zirconium ions and induces an amorphous-to-crystalline transition, with the formation of highly textured monoclinic ZrO2 (P21/c) nanocrystallites, without generating destructive stresses or physical defects. Annealing under vacuum (10−4 Pa) partly reduces the oxide to Zr metal, with the concurrent growth of a ZrO2 phase of the same structure and texture but in substantially larger amounts. The impact of these new findings, with detailed understanding of the abnormal ionic transport, paradoxical oxide growth, and phase-transition effects, is considered, focusing on specific applications relating to surface finishing, electronics, optics, and biomedicine.

Eukaryotic cells assemble an actomyosin ring during cytokinesis to function as a force-generating machine to drive membrane invagination, and to counteract the intracellular pressure and the cell surface tension. It is unclear whether additional factors such as the extracellular matrix (cell wall in yeasts and fungi) affect the actomyosin ring contraction. While studying the fission yeast β-glucan synthase mutant cps1-191, which is defective in division septum synthesis and actomyosin ring contraction, we found that significantly weakening of the extracellular glycan matrix caused the spheroplasts to divide at the non-permissive condition. This division was dependent on a functional actomyosin ring and vesicular trafficking, but independent of normal septum synthesis. cps1-191 cells with weakened extracellular glycan matrix divide non-medially with a much slower ring contraction rate compared to wild type cells under similar conditions, which we term as cytofission. Interestingly, the high turgor pressure appears to play minimal roles in inhibiting ring contraction in cps1-191 mutants as decreasing the turgor pressure alone does not enable cytofission. We propose that during cytokinesis, the extracellular glycan matrix restricts actomyosin ring contraction and membrane ingression, and remodeling of the extracellular components through division septum synthesis relieves the inhibition and facilitates actomyosin ring contraction.

To demonstrate the importance of sample preparation used in Fourier transform infrared (FTIR) spectroscopy of microbiological materials, bacterial biomass samples with and without grinding and after different drying periods (1.5–23 h at 45 °C), as well as biogenic selenium nanoparticles (SeNPs, without washing and after one to three washing steps) were comparatively studied by transmission FTIR spectroscopy. For preparing bacterial biomass samples, Azospirillum brasilense Sp7 and A. baldaniorum Sp245 (earlier known as A. brasilense Sp245) were used. The SeNPs were obtained using A. brasilense Sp7 incubated with selenite. Grinding of the biomass samples was shown to result in slight downshifting of the bands related to cellular poly-3-hydroxybutyrate (PHB) present in the samples in small amounts (under ~10%), reflecting its partial crystallisation. Drying for 23 h was shown to give more reproducible FTIR spectra of bacterial samples. SeNPs were shown to contain capping layers of proteins, polysaccharides and lipids. The as-prepared SeNPs contained significant amounts of carboxylated components in their bioorganic capping, which appeared to be weakly bound and were largely removed after washing. Spectroscopic characteristics and changes induced by various sample preparation steps are discussed with regard to optimising sample treatment procedures for FTIR spectroscopic analyses of microbiological specimens.

International audience; CD4+ T cell trafficking is a fundamental property of adaptive immunity. In this study, we uncover a novel role for histone deacetylase 1 (HDAC1) in controlling effector CD4+ T cell migration, thereby providing mechanistic insight into why a T cell-specific deletion of HDAC1 protects against experimental autoimmune encephalomyelitis (EAE). HDAC1-deficient CD4+ T cells downregulated genes associated with leukocyte extravasation. In vitro, HDAC1-deficient CD4+ T cells displayed aberrant morphology and migration on surfaces coated with integrin LFA-1 ligand ICAM-1 and showed an impaired ability to arrest on and to migrate across a monolayer of primary mouse brain microvascular endothelial cells under physiological flow. Moreover, HDAC1 deficiency reduced homing of CD4+ T cells into the intestinal epithelium and lamina propria preventing weight-loss, crypt damage and intestinal inflammation in adoptive CD4+ T cell transfer colitis. This correlated with reduced expression levels of LFA-1 integrin chains CD11a and CD18 as well as of selectin ligands CD43, CD44 and CD162 on transferred circulating HDAC1-deficient CD4+ T cells. Our data reveal that HDAC1 controls T cell-mediated autoimmunity via the regulation of CD4+ T cell trafficking into the CNS and intestinal tissues.

In the biomass of A. thiophilum BV-S grown in the presence of 7 mM Na2SO4, Raman spectroscopy showed a peak at 348 cm–1 (Se–S bond) in addition to a peak at 250 cm–1 (amorphous modification of Se).

Possible mechanisms of selenite reduction by bacteria of the genus Azospirillum are studied. A method is proposed for producing extracellular Se nanoparticles homogeneous by size which have been characterised by various methods.

Examples are considered of using molecular spectroscopy techniques (Fourier transform infrared, Raman and Mössbauer spectroscopies) in monitoring the responses of bacteria to stresses.

Microbial bio-transformations of the essential trace element selenium are now recognized to occur among a wide variety of microorganisms. These transformations are used to convert this element into its assimilated form of selenocysteine, which is at the active center of a number of key enzymes, and to produce selenium nanoparticles, quantum dots, metal selenides, and methylated selenium species that are indispensable for biotechnological and bioremediation applications. The focus of this review is to present the state-of-the-art of all aspects of the investigations into the bacterial transformations of selenium species, and to consider the characterization and biotechnological uses of these transformations and their products.

Microbial cells are well known to be capable of remaining viable when desiccated, and a variety of beneficial microorganisms can thus be preserved for storage. For the ubiquitous widely studied soil bacterium Azospirillum brasilense (wild-type strain Sp7), which has a significant agrobiotechnological potential owing to its plant-growth-promoting capabilities perspective for its use in biofertilisers, Fourier transform infrared (FTIR) spectroscopy (in the diffuse reflectance mode, DRIFT) was used to control the state of biomass, together with 57Fe transmission Mossbauer spectroscopy to monitor intracellular iron speciation in live rapidly frozen cell suspension and in the lyophilised biomass (both measured at T = 80 K). It has been shown for the first time that a relatively large part of ferrous iron in live cells (22% of the whole cellular iron pool, represented by two high-spin Fe(II) forms, in the 18-h culture grown on 57Fe(III) complex with nitrilotriacetic acid as the sole source of iron) gets largely oxidised upon lyophilisation. The remaining part of iron(II) in the resulting dry biomass was found to be ca. 3% only. The major part of ferric iron in the dry biomass was shown to be comprised of ferritin-like ferric species (giving a typical magnetically split sextet at T = 5 K), while the iron(III) formed from cellular iron(II) by oxidation in air in the course of drying remained in a paramagnetic state even at T = 5 K. The possibility of intracellular iron(II) oxidation to iron(III) upon desiccation may be a specific natural strategy to avoid cell damage caused by Fenton-type reactions in dormant (frozen, dried) cells. The results obtained may have important implications related to iron speciation and redox transformations in dried bacterial preparations intended for long-term storage.

Raman spectra of liquid water and ice were measured at different temperatures. The intensity of the band assigned to bending vibrations of water molecules was observed to decrease at the liquid-to-solid transition, while the Raman line near 2200 cm−1 showed an anomalously high intensity in the solid phase. A tetrahedral model was used for computer analysis of the observed spectral changes. Quantum-chemical calculations of the structure, normal vibrations and Raman spectra in the harmonic approximation, as well as frequencies and intensities of some vibrations using 1D and 2D potential energy surfaces, were carried out using B3LYP with the cc-pVTZ basis set. The influence of the number of hydrogen bonds on the frequency and Raman activity of the bending vibrations was analyzed. The possibility of hydrogen bond weakening upon excitation of the combined bending-rocking vibration due to the large amplitude of this vibration is considered.

In this review, the unique possibilities are considered of the 57Fe transmission (TMS) and 57Co emission (EMS) variants of Mossbauer (nuclear γ-resonance) spectroscopy as nondestructive techniques with minimal sample preparation/treatment and a significant analytical potential, with a focus on the analysis of cation-binding sites in metalloproteins. The techniques are shown to provide unique structural and quantitative information on the coordination microenvironment, the chemical state and transformations of the Mossbauer nuclides in sophisticated metal-containing proteins, including those within complicated supramolecular structures, and in microbial cells or tissues. Recent representative examples of analyses of Fe-containing proteins by 57Fe TMS are briefly discussed, along with the newly emerging data on using 57Co EMS for probing the structural organisation of 57Co-doped cation-binding sites in sophisticated biocomplexes including metalloenzymes. Finally, some rare or exotic applications of Mossbauer spectroscopy (including the synchrotron-based methodology) in protein-related studies are outlined.

Severe accidents in NPP with VVER can be accompanied by hydrogen entering the containment space. The aim of the present work is an experimental and computational study of the possibility of hydrogen stratification in the containment in a scenario replicating the sequence of events occurring during a severe accident with hydrogen emission in a light-water reactor taking account of the impact of accident control on the distribution of a light gas. Euratom and the government corporation Rosatom performed the studies as part of two parallel projects – ERCOSAM and SAMARA. The experimental studies show that heat exchangers aand recombiners do bring about complete mixing of the light gas; a sprinkler system affords mixing of the stratified layer. The experimental studies confirm the results of numerical modeling.

Biofilms are spatially and metabolically structured communities of microorganisms, representing a mode of their existence which is ubiquitous in nature, with cells localised within an extracellular biopolymeric matrix, attached to each other, at an interface. For plant-growth-promoting rhizobacteria (PGPR), the formation of biofilms is of special importance due to their primary localisation at the surface of plant root systems. In this work, FTIR spectroscopy was used, for the first time for bacteria of the genus Azospirillum , to comparatively study 6-day-mature biofilms formed on the surface of ZnSe discs by the rhizobacterium Azospirillum brasilense Sp245 and its mutant A. brasilense Sp245.1610. The mutant strain, having an Omegon Km insertion in the gene of lipid metabolism fabG1 on the plasmid AZOBR_p1, as compared to the wild-type strain Sp245 (see http://dx.doi.org/10.1134/S1022795413110112 ), had previously been shown to possess alterations in the synthesis of fatty acids, as well as in the amount of biomass and relative content of lipopolysaccharide antigens in mature biofilms formed at a hydrophilic or hydrophobic surface (see http://dx.doi.org/10.1134/S002626171602017X ). The 6-day biofilm of the wild-type strain A. brasilense Sp245 was found to contain moderate amounts of poly-3-hydroxybutyrate (PHB, a reserve biopolyester) featured by its typical bands (e.g., the ester carbonyl stretching mode at 1732 cm −1 ), while its mutant strain showed a diminished PHB content in the biofilm (the observed differences were also confirmed by analysing the second derivatives of the FTIR spectra). Thus it may be assumed that in this mutant strain, PHB synthesis is also affected which, in turn, can affect the formation and stability of biofilms.

Microbially driven reduction of selenium oxyanions to elementary selenium, often in the form of nanoparticles (NPs), is widespread in nature. A diversity of possible applications of such biogenic NPs, including those in nanobiotechnology, as well as the specificity of methodologies and mechanisms of their formation via “green synthesis” are very attractive features justifying further studies of the processes of selenium oxyanion bioreduction and the resulting Se 0 nanostructures. In this study, live biomass of the rhizobacterium Azospirillum brasilense Sp7 (harvested after the logarithmic growth phase and washed from culture medium components) was used to obtain extracellular Se NPs relatively homogeneous in size (with average diameters within 50–100 nm) in the process of selenite reduction. Both the control cultures of A. brasilense Sp7 and those incubated with SeO 3 2− (producing Se NPs), as well as the resulting separated Se NPs were studied using Fourier transform infrared (FTIR) spectroscopy in the transmission mode (measured as dried layers on a ZnSe disc), in addition to transmission electron microscopy (TEM), to compare metabolic changes in cells and the bioorganic layers associated with the Se NPs. In the control culture (stored for 24 h in physiological saline), FTIR spectroscopic signs of poly-3-hydroxybutyrate (a ‘reserve’ biopolyester) were observed as a response to the lack of nutrients (trophic stress), whereas they were virtually absent in cells incubated for 24 h in physiological saline with 10 mM SeO 3 2− (toxicity stress). FTIR spectra of Se NPs separated from bacterial cells showed bands typical of proteins, polysaccharides and lipids associated with the particles (in line with their TEM images showing a thin layer over the NPs), in addition to strong carboxylate bands, which evidently stabilise the NP structure and morphology.

The features of porous anodic Al2O3 formation process in galvanostatic regime in selenic acid based electrolyte under a range of anodization conditions were investigated. The growth process kinetics of porous anodic Al2O3 was characterized by chronopotentiometric curves. The effect of electrolyte concentration, current density and anodization duration on the oxide porous structure ordering was studied by scanning electron microscopy. Approximate regions of self-ordered porous Al2O3 formation process conditions were estimated. It was found that anodization parameters, at which self-ordered porous structure formation is observed, correspond to the conditions of equilibrium of oxidation and etching rates. It is shown that deviations from these conditions lead to the disordering of the porous structure.

In the emission (57Co) variant of Mossbauer spectroscopy (EMS), the 57Co radionuclide (with a half-life of 9months) is used that undergoes a nuclear decay 57Co→57Fe via electron capture followed by the emission of a γ-quantum, the energy of which is modified by the chemical state and the close coordination environment of the parent 57Co atom. While EMS has been used largely in materials science and nuclear chemistry, its high sensitivity can also be of great advantage in revealing fine structural features and for speciation analysis of biological complexes, whenever the 57Co2+ cation can be used directly as the coordinating metal or as a substitute for native cobalt or other metal ions. As such EMS applications are yet rare, in order to reliably interpret emission spectra of sophisticated 57Co2+-doped biosystems, model EMS studies of simple cobalt biocomplexes are necessary. In this work, EMS spectroscopic data are analysed and discussed for 57Co2+ complexes with a range of small biomolecules of different structures, including 4-n-hexylresorcinol, homoserine lactone and a few amino acids (spectra measured in rapidly frozen dilute aqueous solutions or in the dried state at T=80K). The EMS data obtained are discussed with regard to the available literature data related to the coordination modes of the biocomplexes under study.

Monitoring of poly-3-hydroxybutyrate accumulation and changes in its relative contents in biomass of the plant-growth-promoting bacteria Azospirillum brasilense (strains Sp7, Cd and Sp245) was performed during aerobic cultivation for 1 to 8 days at various initial concentrations of bound nitrogen (0.1 to 0.5 g∙L–1 NH4Cl) in the culture medium using in-situ transmission FTIR spectroscopy. A methodology has been proposed based on calculating band areas in FTIR spectra (instead of band intensities commonly used earlier) for determining relative contents of PHB in dry bacterial biomass, using the ester ν(C=O) band as a PHB marker (in the region 1750–1720 cm−1) and amide II band of cellular proteins (at ca. 1540 cm−1). Differences in PHB accumulation levels and their changes in the course of cultivation under various trophic stress for the three strains are discussed in relation to their different ecological niches which they occupy in the rhizosphere.

For the ubiquitous diazotrophic rhizobacterium Azospirillum brasilense, which has been attracting the attention of researchers worldwide for the last 35 years owing to its significant agrobiotechnological and phytostimulating potential, the data on iron acquisition and its chemical speciation in cells are scarce. In this work, for the first time for azospirilla, low-temperature (at 80 K, 5 K, as well as at 2 K without and with an external magnetic field of 5 T) transmission Mössbauer spectroscopic studies were performed for lyophilised biomass of A. brasilense (wild-type strain Sp7 grown with (57)Fe(III) nitrilotriacetate complex as the sole source of iron) to enable quantitative chemical speciation analysis of the intracellular iron. In the Mössbauer spectrum at 80 K, a broadened quadrupole doublet of high-spin iron(III) was observed with a few percent of a high-spin iron(II) contribution. In the spectrum measured at 5 K, a dominant magnetically split component appeared with the parameters typical of ferritin species from other bacteria, together with a quadrupole doublet of a superparamagnetic iron(III) component and a similarly small contribution from the high-spin iron(II) component. The Mössbauer spectra recorded at 2 K (with or without a 5 T external field) confirmed the assignment of ferritin species. About 20% of total Fe in the dry cells of A. brasilense strain Sp7 were present in iron(III) forms superparamagnetic at both 5 and 2 K, i.e. either different from ferritin cores or as ferritin components with very small particle sizes.

The hydrogen trioxide (HT) molecule HOOOH is 1) a prototype for a class of molecules of the form X(ZY)2 with two equivalent internal tops (ZY) and 2) the second representative of the polyoxides series of the form HOnH (n ≥ 2). Due to this, it is the subject of close attention of researchers. In this paper, we performed a group theory analysis of the torsional and spin states of the HOOOH, DOOOH, and DOOOD molecules. The relationships have been established between the symmetry species of the C2V(M) molecular symmetry group to which the HOOOH and DOOOD molecules belong, and the symmetry species of the C2 and CS point groups to which the equilibrium configurations of trans- and cis-conformers of the above molecules belong, respectively. 2D PES and 2D surfaces of kinematic coefficients related to torsional vibrations of hydroxyl groups were calculated at the complete basis set (CBS) limit by extrapolating the results of calculations at the MP2/cc-pVTZ and MP2/cc-pVQZ levels of theory. For all the three molecules, the energies of the stationary torsional states were computed using the Fourier method for a numerical solution of the 2D vibrational Schrodinger equation. Symmetry species of torsional states and the values of quantum numbers defining the types of torsional vibrations were found by analyzing the torsional wave functions. The selection rules for transitions between torsional states in the dipole approximation were also formulated.

Microbial reduction of selenium oxyanions has attracted attention in recent years. In this study, an original and simple method for the synthesis of extracellular selenium nanoparticles (Se NPs) of relatively uniform size has been developed using strains Sp7 and Sp245 of the ubiquitous plant-growth promoting rhizobacterium Azospirillum brasilense, both capable of selenite (SeO32−) reduction. In addition, a reliable purification protocol for the recovery of the Se NPs has been perfected, which could be applied with minor modifications to cultures of other microbial species. Importantly, it was found that, by changing the conditions of bacterial reduction of selenite, extracellularly localised Se NPs can be obtained using bacteria which would otherwise produce intracellular Se NPs. In particular, bacterial cultures grown up to the end of the logarithmic growth phase, washed free of culture medium and then incubated with selenite, were used to obtain extracellular Se NPs. Their sizes depended on the initial selenite concentration (∼25–80 nm in diameter at 50–10 mM selenite, respectively). The Se NPs obtained were characterised by transmission electron microscopy (TEM), dynamic light scattering, as well as Raman and UV–vis spectroscopies. Their zeta potential was found to be negative (ca. minus 21–24 mV). Bacterial selenite reduction was also studied in the presence of the efflux pump inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP). In this case, TEM indicated the formation only of intracellular selenium crystallites. The data show that the formation of extracellular Se NPs requires normal bacterial metabolic activity, while CCCP evidently blocks the membrane export of Se0 nuclei.

The transmission (57Fe) and emission (57Co) variants of Mossbauer spectroscopy are used to monitor metabolic transformations of 57FeIII/57FeII and 57CoII in cells of the bacterium Azospirillum brasilense Sp7. (The spectra are measured at 80 K.) For 57CoII, metabolic changes in the living cells are observed after 1 h. Two components of high-spin 57FeII are observed for the bacteria grown with 57FeIII as a source of iron; the parameters for 57FeIII correspond to ferritin-like components.

Chemically modified pectin derivatives obtained by partial esterification of its hydroxyl moieties with fatty acids (FA; oleic, linoleic and palmitic acids), as well as the initial apple peel pectin were comparatively characterised using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Characteristic changes observed in DRIFT spectra in going from pectin to its FA esters are related to the corresponding chemical modifications. Comparing the DRIFT spectra with some reported data on FTIR spectra of the same materials measured in KBr or NaCl matrices has revealed noticeable shifts of several polar functional groups both in pectin and in its FA-esterified products induced by the halide salts. The results obtained have implications for careful structural analyses of biopolymers with hydrophilic functional groups by means of different FTIR spectroscopic methodologies.

A set of experimental data obtained by Fourier transform infrared (FTIR) spectroscopy (involving the use of samples ground and pressed with KBr, i.e. in a polar halide matrix) and by matrix-free transmission FTIR or diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic methodologies (involving measurements of thin films or pure powdered samples, respectively) were compared for several different biomacromolecular substances. The samples under study included poly-3-hydroxybutyrate (PHB) isolated from cell biomass of the rhizobacterium Azospirillum brasilense; dry PHB-containing A. brasilense biomass; pectin (natural carboxylated heteropolysaccharide of plant origin; obtained from apple peel) as well as its chemically modified derivatives obtained by partial esterification of its galacturonide-chain hydroxyl moieties with palmitic, oleic and linoleic acids. Significant shifts of some FTIR vibrational bands related to polar functional groups of all the biomacromolecules under study, induced by the halide matrix used for preparing the samples for spectroscopic measurements, were shown and discussed. A polar halide matrix used for preparing samples for FTIR measurements was shown to be likely to affect band positions not only per se, by affecting band energies or via ion exchange (e.g., with carboxylate moieties), but also by inducing crystallisation of metastable amorphous biopolymers (e.g., PHB of microbial origin). The results obtained have important implications for correct structural analyses of polar, H-bonded and/or amphiphilic biomacromolecular systems using different methodologies of FTIR spectroscopy.

Vibrational (Fourier transform infrared (FTIR) and Raman) spectroscopic techniques can provide unique molecular-level information on the structural and compositional characteristics of complicated biological objects. Thus, their applications in microbiology and related fields are steadily increasing. In this communication, biogenic selenium nanoparticles (Se NPs) were obtained via selenite (SeO32-) reduction by the bacterium Azospirillum thiophilum (strain VKM B-2513) for the first time, using an original methodology for obtaining extracellular NPs. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed the Se NPs to have average diameters within 160-250nm; their zeta potential was measured to be minus 18.5mV. Transmission FTIR spectra of the Se NPs separated from bacterial cells showed typical proteinacious, polysaccharide and lipid-related bands, in line with TEM data showing a thin layer covering the Se NPs surface. Raman spectra of dried Se NPs layer in the low-frequency region (under 500cm-1 down to 150cm-1) showed a single very strong band with a maximum at 250cm-1 which, in line with its increased width (ca. 30cm-1 at half intensity), can be attributed to amorphous elementary Se. Thus, a combination of FTIR and Raman spectroscopic approaches is highly informative in non-destructive analysis of structural and compositional properties of biogenic Se NPs.

Biogenic formation of nano-sized particles composed of various materials (in particular, selenium) by live microorganisms is widespread in nature. This phenomenon has been increasingly attracting the attention of researchers over the last decade not only owing to a range of diverse applications of such nanoparticles (NPs) in nanobiotechnology, but also because of the specificity of methodologies and mechanisms of NPs formation related to "green synthesis". In this mini-review, recent data are discussed on the multifaceted role of proteins in the processes of microbial reduction of selenium oxyanions and the formation of Se NPs. Besides the involvement of proteins in reducing selenites and selenates, their participation in the microbially driven growth and stabilisation of Se NPs is analysed, which results in the formation of unique nanostructured materials differing from those obtained chemically. This mini-review is thus focussed on proteins involved in microbial synthesis of Se NPs and on instrumental analysis of these processes and their products (biogenic nanostructured selenium particles functionalised by a surface-capping layer of various biomacromolecules).

The levels and compartmentalization of Na, Mg, Al, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Sr, Mo, Sb, I, Cs, Ba, La, Ce, Sm, Eu, Tb, Hf, Ta, Au, Th, and U in Phragmites australis Carex conescens L and Cladophora sericea from the Caucasian coast of the Black Sea Anapa recreational region was investigated by Neutron Activation Analysis. The study touches upon subject of the sediment-to-plant and root-to-leaf elemental transfer as well as of the influence of anthropogenic pollution on wetland ecosystems in zone of resort. The content of the majority of considered elements was found higher in the belowground organs of P. australis than in the aboveground tissues while a reverse regularity was evidenced for C. conescens. The levels of elements decrease from bottom sediments to aquatic plants with the notable exception of the halogens Cl, Br and I that presented 5 to 100 fold higher content in plants than in sediments. The increased levels of As, Mo, and Sb in some soil and sediment samples most probably indicate the anthropogenic pollution. It recommends them for a continuous monitoring of the same area.

A series of substituted cyclic acetals were synthesized and tested for their bactericidal activity against bacteria strain Azospirillum brasilense Sp245.

The results of a comparative study of two samples of the rhizobacterium Azospirillum brasilense (strain Sp245) prepared in different conditions and of human liver ferritin using Mossbauer spectroscopy with a high velocity resolution demonstrated the presence of ferritin-like iron (i.e. iron similar to that found in ferritin-like proteins) in the bacterium. Mossbauer spectra of these samples were fitted in two ways: as a rough approximation using a one quadrupole doublet fit (the homogeneous iron core model) and using a superposition of quadrupole doublets (the heterogeneous iron core model). Both results demonstrated differences in the Mossbauer parameters for mammalian ferritin and for bacterial ferritin-like iron. Moreover, some differences in the Mossbauer parameters were observed between the two samples of A. brasilense Sp245 related to the differences in their preparation conditions.

Iron(III)-containing aqueous solutions of 5-methylresorcinol (5-MR), 5-n-propylresorcinol (5-n-PR) and 4-n-hexylresorcinol (4-n-HR) at pH ~ 3 were studied by means of 57Fe transmission Mossbauer spectroscopy. Kinetic considerations were applied to the redox reactions. Density Functional Theory (DFT) calculations were performed for the alkylresorcinol (AR) molecules and their non-alkylated analogue (resorcinol). Mossbauer spectra consisted of quadrupole doublets assigned to high-spin Fe(III) and Fe(II) species. From changes in their relative spectral areas, a gradual reduction of Fe(III) by all the ARs studied was observed. However, significant differences were found for the reduction rates among the ARs. The following series of the reduction rates was established by means of Mossbauer spectroscopy: 4-n-HR ≫ 5-MR > 5-n-PR, supplemented by rate constants calculated using a kinetic model. DFT calculations resulted in the following series: 4-n-HR ≫ 5-n-PR > 5-MR ≫ resorcinol (the latter is not oxidised under the conditions applied). The reversed order of the experimentally observed 5-MR and 5-n-PR oxidation rates may be explained in terms of their different kinetic parameters related to their structure.

Preliminary 57 Fe transmission Mossbauer spectroscopic data were ob- tained for the first time for live cells of the plant-growth-promoting rhizobacterium Azospirillum brasilense (wild-type strain Sp245) grown aerobically with 57 Fe III - nitrilotriacetate (NTA) complex as a sole source of iron. The results obtained have shown that live cells actively reduce part of the assimilated iron(III) to iron(II), the latter amounting up to 33 % of total cellular iron after 18 h of growth, and 48 % after additional 3 days of storage of the dense wet cell suspension in nutrient-free saline solution in air at room temperature (measured at 80 K). The cellular iron(II) was found to be represented by two quadrupole doublets of different high-spin forms, while the parameters of the cellular iron(III) were close to those typical for bacterioferritins.

Mossbauer spectroscopy is used for a comparative study of the rate of iron(III) reduction by 4-n-hexylresorcinol (4-n-HR, a chemical analog of microbial autoregulators excreted by cells into the environment that allow intercellular communication) in aqueous media in the pH range of 1.5–4.5 simulating acidic soil conditions. The concomitant process of 4-n-HR oxidation is monitored using UV spectrophotometry.

Effect of selenium(+4) as selenite (Se32−) on two Azospirillum brasilense strains, which occupy different ecological niches (an epiphyte Sp7 and a facultative endophyte Sp245), was studied. The cultures grown in the medium with sodium selenite exhibited intense red coloration. Transmission electron microscopy and X-ray fluorescence analysis revealed accumulation of elementary selenium within the cells of both strains as nanoparticles 50–400 nm in diameter. The ability to reduce inorganic selenium(+4) to elementary selenium (as nanoparticles) has not been previously reported for azospirilla. Our results indicate the possibility to apply Azospirillum strains as microsymbionts for phytoremediation of, and cereal cultivation on, selenium-contaminated soils. The ability of azospirilla to synthesize selenium nanoparticles may be of interest for nanobiotechnology.

An assessment of the present status of sites used for peaceful underground nuclear explosions on the territory of the Russian Federation is given. The desirability of recognizing the central zones of nuclear explosions and surface repositories formed near them for storing special radwastes is substantiated. It is shown that formation water is the main substance for removing technogenic radionuclides to the Earth’s surface as well as upper-lying water-bearing levels. Data are presented on the present radio-ecological status of the territories of peaceful nuclear explosions and their possible classification according to the degree of radiation safety.

The integral bioluminescence (BL) intensity of live Photobacterium phosphoreum cells (strain 1883 IBSO), sampled at the stationary growth stage (20 h), was monitored for further 300 h in the absence (control) and presence of (241)Am (an α-emitting radionuclide of a high specific activity) in the growth medium. The activity concentration of (241)Am was 2 kBq l(-1); [(241)Am]=6.5×10(-11) M. Parallel experiments were also performed with water-soluble humic substances (HS, 2.5 mg l(-1); containing over 70% potassium humate) added to the culture medium as a possible detoxifying agent. The BL spectra of all the bacterial samples were very similar (λ(max)=481±3 nm; FWHM=83±3 nm) showing that (241)Am (also with HS) influenced the bacterial BL system at stages prior to the formation of electronically excited states. The HS added per se virtually did not influence the integral BL intensity. In the presence of (241)Am, BL was initially activated but inhibited after 180 h, while the system (241)Am+HS showed an effective activation of BL up to 300 h which slowly decreased with time. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, applied to dry cell biomass sampled at the stationary growth phase, was used to control possible metabolic responses of the bacteria to the α-radioactivity stress (observed earlier for other bacteria under other stresses). The DRIFT spectra were all very similar showing a low content of intracellular poly-3-hydroxybutyrate (at the level of a few percent of dry biomass) and no or negligible spectroscopic changes in the presence of (241)Am and/or HS. This assumes the α-radioactivity effect to be transmitted by live cells mainly to the bacterial BL enzyme system, with negligible structural or compositional changes in cellular macrocomponents at the stationary growth phase.

Изучено влияние селена в степени окисления +4, селенита (SeO ), на два штамма Azospirillum brasilense, отличающиеся занимаемыми экологическими нишами – эпифит Sp7 и факультативный эндофит Sp245. При выращивании культур в присутствии селенита натрия было зафиксировано интенсивное красное окрашивание бактерий. С использованием просвечивающей электронной микроскопии и рентгенофлуоресцентного анализа было показано накопление элементарного селена клетками обоих штаммов внутриклеточно в виде наночастиц диаметром 50–400 нм. Впервые для бактерий рода Azospirillum обнаружена способность восстанавливать неорганический селен в степени окисления +4 до элементарного селена (с образованием наночастиц). Полученные результаты указывают на возможность использования азоспирилл как микросимбионтов в процессах фиторемедиации и при культивировании злаковых на загрязненных соединениями селена почвах. Способность азоспирилл синтезировать наночастицы селена может представлять интерес для нанобиотехнологии.

Thermoplastic linear ionomer based on sulphonated poly(ether-urethane)—styrene-acrylate copolymer, doped with natural Fe2 + , was studied by Mossbauer spectroscopy at T = 78 and 290 K to monitor the chemical state of Fe species. The Fe2 + added to aqueous suspension of the system was only partly oxidised in the course of polymer film preparation and drying in air. The oxidised part comprised a magnetic phase (~19 % of total Fe both at T = 78 and 298 K) and a quadrupole doublet (~40 %), while FeII (over 40 %) stabilised in two types of microenvironments.

Literature analysis and chemical considerations of biological phosphate solubilization have shown that the commonly used selection factor for this trait, tricalcium phosphate (TCP), is relatively weak and unreliable as a universal selection factor for isolating and testing phosphate-solubilizing bacteria (PSB) for enhancing plant growth. Most publications describing isolation of PSB employed TCP. The use of TCP usually yields many (up to several thousands per study) isolates “supposedly” PSB. When these isolates are further tested for direct contribution of phosphorus to the plants, only a very few are true PSB. Other compounds are also tested, but on a very small scale. These phosphates (P), mainly Fe-P, Al-P, and several Ca-P, are even less soluble than TCP in water. Because soils greatly vary by pH and several chemical considerations, it appears that there is no metal-P compound that can serve as the universal selection factor for PSB. A practical approach is to use a combination of two or three metal-P compounds together or in tandem, according to the end use of these bacteria—Ca-P compounds (including rock phosphates) for alkaline soils, Fe-P and Al-P compounds for acidic soils, and phytates for soils rich in organic P. Isolates with abundant production of acids will be isolated. This approach will reduce the number of potential PSB from numerous isolates to just a few. Once a potential isolate is identified, it must be further tested for direct contribution to P plant nutrition and not necessarily to general growth promotion, as commonly done because promotion of growth, even by PSB, can be the outcome of other mechanisms. Isolates that do not comply with this general sequence of testing should not be declared as PSB.

Intracellular accumulation of poly-3-hydroxybutyrate (PHB) was comparatively studied in the plant-growth-promoting bacterium (PGPB) Azospirillum brasilense (epiphytic strain Sp7 and endophytic strain Sp245) grown microaerobically for 2 days under nitrogen deficiency in the standard malate salt medium in the absence (control) or presence of copper (0.1 mM Cu2+). For quantitative determination of PHB content of cells, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy of whole-cell biomass samples was used. After 2 days in control cells, PHB accumulation in strain Sp7 reached ca. 24% of dry cell mass (d.c.m.). In strain Sp245, the PHB content in the control was over 1.3-fold higher (32% d.c.m.) than in strain Sp7. In the presence of copper(II), PHB accumulation was notably enhanced in strain Sp7 (over 1.6-fold, up to ca. 39% d.c.m.), whereas in strain Sp245 it changed insignificantly (from 32% up to ca. 35% d.c.m.). The levels of copper(II) uptake were comparable in both strains. These findings are in line with our earlier observations that even in rich NH4+-supplemented medium, some heavy metals, including copper(II), induce PHB biosynthesis in A. brasilense strain Sp7, but not in Sp245. The dissimilarities in the levels of PHB accumulation and in the effects induced by copper(II) in the two strains are attributed to their different adaptive potentials owing to different ecological niches they occupy in the rhizosphere.

Emission (57Co) Mossbauer spectra of the aspartic acid—57CoCl2 system were measured at T = 80 K in frozen aqueous solution and in the form of a dried residue of this solution. The Mossbauer spectra, besides a weak contribution from after-effects, showed two Fe2 + /Co2 + components which were ascribed to octahedrally and tetrahedrally coordinated 57CoII microenvironments in the Asp–cobalt(II) complex. This dual coordination mode may be due to the involvement of the second terminal carboxylic group of aspartic acid in the coordination sphere of Co.

Research into ion-exchange properties of cell walls isolated from thallus of red seaweed Phyllophora crispa was carried out. Ion-exchange capacity and the swelling coefficient of the red alga cell walls were estimated at various pH values (from 2 to 12) and at constant ionic strength of a solution (10 mM). It was established that behavior of cell walls as ion-exchangers is caused by the presence in their matrix of two types of cation-exchange groups and amino groups. The amount of the functional group of each type was estimated, and the corresponding values of pK(a) were calculated. It can be assumed that ionogenic groups with pK(a) -5 are carboxyl groups of uronic acids, and ionogenic groups with pK(a) -7.5 are carboxyl groups of the proteins. Intervals of pH in which cation-exchange groups are ionized and can take part in exchange reactions with cations in the environment are defined. It was found that protein was a major component of cell wall polymeric matrix because its content was 36%.

Mossbauer spectroscopy was used to study iron(III) reduction by alkylresorcinols (ARs; i.e., chemical analogs of microbial autoregulators excreted by cells into the environment and involved in intercellular communication) in aqueous solutions simulating acidic soil conditions. The concomitant oxidation process for an AR (5-methylresorcinol) was monitored using UV spectrophotometry.

Diverse processes of microbial remote intercellular communication as well as the exchange of molecular signals between microbial cells and their host macroorganisms, involving specific low-molecular-mass diffusible substances (used as a ‘chemical language’), are at the peak of current research in biosciences. This fundamental interest is due to the unique possibility of controlling the microbial behaviour and metabolism by influencing merely their signalling pathways. On the other hand, abiotic impact of the environment (medium) on extracellular molecular signals is also of great importance, as any of their chemical interactions (e.g., complexation or oxidation) represent direct interferences in the process of ‘signal delivery’ through the medium. In this work, chemical interactions of microbial extracellular molecular signals (alkylresorcinols (AR), homoserine lactone (HL) – chemical analogues of microbial autoregulatory substances) with iron(III) were monitored using freeze-quench 57 Fe Mossbauer spectroscopy in moderately acidic aqueous solutions as well as in the dried solids obtained thereof. The conditions applied were designed to simulate possible processes occurring in soils, where ferric iron is commonly ubiquitous. Gradual reduction of iron(III) by AR was observed, coupled to oxidative degradation of the organics, in solution, while iron(II) also remained dominant upon drying, whereas for HL, some iron(II) was detected in the dried solid only. The iron(III) reduction rate in solution for AR with a longer alkyl chain (4- n -C 6 ) was found to be much higher than that for the methyl (5-C 1 )-substituted derivative, pointing to the importance of the structure (i.e., the position and/or the nature of the alkyl substituent) of the alkylresorcinol molecule for the redox process rate. The results obtained indicate that ARs can be readily oxidised abiotically by soil iron(III) in moderately acidic media, thus being excluded from signalling pathways, which is equal to “message undelivery”, directly affecting microbial autoregulation.

Thermoplastic linear poly(ether-urethane) sulphonated ionomer (PEUSI), doped with natural Fe2 + , was studied by Mossbauer spectroscopy at T = 78 and 290 K in order to monitor the chemical state of Fe species. The Fe2 + added was found to get only partly oxidised in the course of preparation of a dry polymer film from aqueous suspension. The oxidised part gave a ferric quadrupole doublet (over half of total Fe added) and, at T = 78 K only, a small portion of magnetically split sextet (ca. 3%), whereas FeII (total over 40%) stabilised in two different forms (represented by quadrupole doublets) corresponding to two types of iron(II) microenvironments, where FeII could be coordinated involving –CONH– and –NHNH– moieties and sulphonate groups in PEUSI. The results obtained show that Fe2 + -doping of PEUSI-based materials may be used for probing their structural characteristics by Mossbauer spectroscopy.