Ab initio calculations of the crystal field and phonon dispersions in CePd2Al2 and LaPd2Al2.

CePd2Al2 crystallizes in the CaBe2Ge2-type tetragonal structure (P4/nmm, 129) and undergoes a phase transition to the orthorhombic Cmme structure at around 13 K. Its inelastic neutron spectra reveal an additional magnetic excitation that was ascribed to electron-phonon interaction leading to a formation of a new quantum quasi-bound vibron state. We present the first-principles calculations of the crystal field excitations and lattice dynamics calculations of the phonon dispersions to compare with the experimental data. The calculated crystal field energy splitting in CePd2Al2 agrees well with the model used to describe the experimental neutron scattering spectra. The first excited crystal field level moves to higher energies when undergoing the transformation from tetragonal to orthorhombic structure, in agreement with the experiment. The analysis based on calculated elastic constants and lattice dynamics calculations show that in both tetragonal and orthorhombic structures there are no imaginary modes for any q-wave vector within the Brillouin zone, and therefore the lattice structures are stable. The phonon dispersions and density of states are calculated for both crystal structures of CePd2Al2 and its nonmagnetic counterpart LaPd2Al2. The results generally agree well with the experimental data including the high phonon density of states around 12 meV. The phonon density of states is also used to calculate the mean squared displacement, Debye temperature, lattice heat capacity and compared with similar properties of the available experiment.

Establishment of Lactobacillus plantarum strain in honey bee digestive tract monitored using gfp fluorescence.

Lactic acid bacteria are symbiotic bacteria that naturally reside in the gastrointestinal tract of honey bees. They serve a multitude of functions and are considered beneficial and completely harmless. In our experiments Lactobacillus plantarum strain B35, isolated from honey bee digestive tract, was modified using pAD43-25 plasmid carrying a functional GFP gene sequence (gfpmut3a) and used as a model for monitoring and optimisation of the mode of application. The establishment of this strain in honey bee digestive tract was monitored using GFP fluorescence. Three different modes of oral application of this strain were tested: water suspension of lyophilised bacteria, aerosol application of these bacteria and consumption of sugar honey paste containing the lyophilised lactobacilli. Two days after administration the L. plantarum B35-gfp was present throughout the honey bee digestive tract with 104-105 cfu/bee with highest count observed for aerosol application.

The development of specific heat and electrical resistivity in the CeNi(x)Pd(1-x)In series.

Our report describes the anomalous electronic behavior of CeNi(x)Pd(1-x)In compounds studied by specific heat and electrical resistivity measurements. These compounds belong to the large and relatively thoroughly studied group of ternary rare-earth intermetallics crystallizing in the ZrNiAl-type structure. The investigated series shows a transition from the heavy fermion antiferromagnetic system of CePdIn to the valence fluctuating state observed in CeNiIn. The isostructural and isoelectronic substitution of Pd by Ni leads to a change in the character of the d-electrons and the lattice parameters of the system because of the smaller radius of Ni atoms. These changes have a great impact on the magnetic properties of the studied compounds. The antiferromagnetic transition shifts first to lower temperatures, from T(N) = 1.7 K for CePdIn to T(N) = 1.3 K for CeNi0.2Pd0.8In. For a Ni content ≥40%, there is no sign of a magnetic phase transition in the specific heat and electrical resistivity data. Moreover, the data indicate anomalous non-Fermi-liquid behavior for concentrations with 0.4 ≤ x ≤ 0.6, which is clearly seen in both types of measurements. The rest of series behaves similarly to the second parent compound CeNiIn. Besides the cerium compounds, superconductivity in LaNi0.2Pd0.8In is also presented.

Staphylococcus nepalensis in the guano of bats (Mammalia).

Thirty randomly selected mesophilic isolates from the six years old guano sample from mixed Myotis myotis and M. blythii summer roosts colony were isolated and identified as Staphylococcus nepalensis using MALDI TOF analysis. 16S rRNA gene sequencing of selected five isolates and subsequent phylogenetic analysis confirmed that all sequences showed the highest similarity to S. nepalensis sequences. Several virulence factors were produced by tested isolates, mainly capsule formation and resistance to tetracycline, ampicillin, gentamycin, and chloramphenicol antibiotics. Our experiments show that the majority of cultivable mesophilic bacteria from the guano of bats belong to the S. nepalensis species. This is the first report on the occurrence of this species in the guano of bats and our results indicate that the guano accumulated near or directly in human dwellings and buildings may represent a significant risk for human health.

Limited genetic diversity of Aerococcus viridans strains isolated from clinical and subclinical cases of bovine mastitis in Slovakia.

The Aerococcus viridans isolates from bovine mastitis in Slovakia were isolated and characterized by classical microbiological and biochemical, and molecular techniques including IGS-PCR and rep-PCR, ARDRA and 16S rDNA gene sequencing. The substantial variability of antibiotic resistance patterns was observed. The majority of strains were resistant to beta-lactam antibiotics, the resistance to tetracycline was observed in 3 tested strains, resistance to lincomycin was found in 4 strains and practically all tested strains were sensitive to neomycin and ciprofloxacin. While variable at a phenotypic level, no significant genetic variability among A. viridans isolates was detected by molecular DNA based methods. The data obtained suggest that a few A. viridans strains spread among cow's population in Slovak farms.

Mosaic structure of the small cryptic plasmid pKST23 from Escherichia coli.

Small plasmid pKST23 was isolated from sheep ruminal Escherichia coli population. Plasmid sequence was determined to be 2,779 bp in length and was found to have an overall 42 % of GC pairs. However, its sequence can be divided into two regions based on genetic composition and the GC content. It was found that the high GC region spanning approximately from nucleotide 1,300 to 2,750 was identical to a group of small Escherichia coli plasmids and encoded a putative replication protein identical to plasmid pKL1 Rep protein. The part with lower GC pairs seemed to be more specific as it showed no similarity to the GenBank database. Computational analysis revealed four open reading frames, two of which showed considerable homology to replication proteins. PCR primers targeting parts of the two different regions of plasmid pKST23 were used to assess the occurrence of related plasmids within ruminal E. coli population.

Variability of Actinobacteria, a minor component of rumen microflora.

Actinobacteria (Actinomycetes) are a significant and interesting group of gram-positive bacteria. They are regular, though infrequent, members of the microbial life in the rumen and represent up to 3 % of total rumen bacteria; there is considerable lack of information about ecology and biology of rumen actinobacteria. During the characterization of variability of rumen treponemas using non-cultivation approach, we also noted the variability of rumen actinobacteria. By using Treponema-specific primers a specific 16S rRNA gene library was prepared from cow and sheep rumen total DNA. About 10 % of recombinant clones contained actinobacteria-like sequences. Phylogenetic analyses of 11 clones obtained showed the high variability of actinobacteria in the ruminant digestive system. While some sequences are nearly identical to known sequences of actinobacteria, we detected completely new clusters of actinobacteria-like sequences, representing probably new, as yet undiscovered, group of rumen Actinobacteria. Further research will be necessary for understanding their nature and functions in the rumen.

Antibiotic resistance and restriction endonucleases in fecal enterococci of chamois (Rupicapra rupicapra Linnaeus, 1758).

Two hundred eighty-four isolates of enterococci from feces of wild living chamois from alpine environments were tested for sensitivity to three antibiotics. Low frequency of resistance was observed in studied enterococcal populations (about 5 % for tetracycline and erythromycin and 0 % for ampicillin). In six animals, the population of enterococci lacked any detectable resistance. Our data indicated that enterococcal population in feces of the majority of studied animals did not encounter mobile genetic elements encoding antibiotic resistance probably due to spatial separation and/or due to low exposure to the antibiotics. Based on resistance profiles observed, three populations were analyzed for the presence of restriction endonucleases. The restriction enzymes from two isolates-31K and 1K-were further purified and characterized. Restriction endonuclease Efa1KI recognizes CCWGG sequence and is an isoschizomer of BstNI. Endonuclease Efc31KI, a BsmAI isoschizomer, recognizes the sequence GTCTC and it is a first restriction endonuclease identified in Enterococcus faecium. Our data indicate that restriction-modification (R-M) systems do not represent an efficient barrier for antibiotic resistance spreading; enterococcal populations colonized by antibiotics resistance genes were also colonized by the R-M systems.

Magnetic phase diagrams of R2RhIn8 (R = Tb, Dy, Ho, Er and Tm) compounds.

We have grown and characterized single crystals of R(2)RhIn(8) (R=Tb, Dy, Ho, Er and Tm) compounds crystallizing in the tetragonal Ho(2)CoGa(8)-type crystal structure. Their magnetic properties were studied by specific heat and magnetization measurements. All the investigated compounds order antiferromagnetically with Néel temperatures of 43.6, 25.1, 10.9, 3.8 and 4.1 K, respectively. Magnetic phase diagrams were constructed.

Lactate dehydrogenase gene variability among predominant lactate utilizing ruminal bacteria.

The inter- and intraspecies variability of lactate dehydrogenase (ldh) gene was determined among the predominant ruminal lactate utilizing bacteria. Nearly complete nucleotide sequences of ldh gene, encoding NAD-dependent lactate dehydrogenase of three Megasphaera elsdenii and six Selenomonas ruminantium strains, were obtained and compared. Phylogenetic analyses revealed a limited variability between the ldh sequences studied. The majority of differences observed were silent mutations at the 3rd position of codons. Surprisingly, the intraspecies diversity of the ldh gene among S. ruminantium isolates was higher than the interspecies level between S. ruminantium and M. elsdenii, which strongly suggests the possibility of acquisition of this gene by horizontal gene transfer.

Fructanolytic and saccharolytic enzymes of the rumen bacterium Pseudobutyrivibrio ruminis strain 3--preliminary study.

P. ruminis strain 3 was isolated from the ovine rumen and identified on the basis of comparison of its 16S rRNA gene with GenBank. The bacterium was able to grow on Timothy grass fructan, inulin, sucrose, fructose and glucose as a sole carbon source, reaching absorbance of population in a range of 0.4-1.2. During 1 d the bacteria exhausted 92-97% of initial dose of saccharides except for inulin (its utilization did not exceed 33%). The bacterial cell extract catalyzed the degradation of Timothy grass fructan, inulin and sucrose in relation to carbon source present in growth medium. Molecular filtration on Sephadex G-150, polyacrylamide gel electrophoresis combined with zymography technique and TLC was used to identify enzymes responsible for the digestion of sucrose and both polymers of fructose. Two specific endolevanases (EC 3.2.1.65), nonspecific beta-fructofuranosidase (EC 3.2.1.80 and/or EC 3.2.1.26) and sucrose phosphorylase (EC 2.4.1.7) were detected in cell-free extract from bacteria grown on Timothy grass fructan.

Variability of treponemes in the rumen of ruminants.

Complete 16S rRNA sequences were determined of recently proposed new species of treponemes designated strain S and T. Sequence comparison indicated that both species belong to the Treponema saccharophilum cluster, having thus at least 5 cultivable representatives. Phylogenetic analysis of available GenBank 16S rRNA sequences revealed two phylogenetically distant treponema clusters (T. saccharophilum cluster and T. bryantii cluster). Surprisingly, while among cultivated treponemes dominate T. saccharophilum cluster members, detailed analysis showed that all treponema-like sequences obtained by culture independent 16S rRNA methods belong to the T. bryantii cluster, from which only two cultivable representatives have so far been known. Meta-analysis of available data revealed that treponemes are an infrequent and minor group of bacteria, representing less than 2.4% of total rumen bacteria.

Phosphorolytic cleavage of sucrose by sucrose-grown ruminal bacterium Pseudobutyrivibrio ruminis strain k3.

Rumen bacterium Pseudobutyrivibrio ruminis strain k3 utilized over 90% sucrose added to the growth medium as a sole carbon source. Zymographic studies of the bacterial cell extract revealed the presence of a single enzyme involved in sucrose digestion. Thin layer chromatography showed fructose and glucose-1-phosphate (Glc1P) as end products of the digestion of sucrose by identified enzyme. The activity of the enzyme depended on the presence of inorganic phosphate and was the highest at the concentration of phosphate 56 mmol/L. The enzyme was identified as the sucrose phosphorylase (EC 2.4.1.7) of molar mass approximately 54 kDa and maximum activity at pH 6.0 and 45 degrees C. The calculated Michaelis constant (Km) for Glc1P formation and release of fructose by partially purified enzyme were 4.4 and 8.56 mmol/L while the maximum velocities of the reaction (Vlim) were 1.19 and 0.64 micromol/L per mg protein per min, respectively.

Bacterial-protozoal interactions in a microbial community of rumen ciliate Entodinium caudatum culture under mercury stress.

We examined the role of rumen ciliates, using Entodinium caudatum as a model organism, in the detoxification of soluble mercury(II) in vitro under conditions with enhanced or reduced diversity of a co-culture bacterial population as well as the effects of long-term mercury(II) stress on in vitro fermentation parameters and major mercury detoxification products. The E. caudatum growth depended on the capability of the co-culture bacterial population to develop resistance to mercury(II) chloride and on culture conditions. The production of fermentation gas was reduced (P < 0.01) in contrast to methane production. Proportions of volatile fatty acids were affected; however, the total concentration of volatile fatty acids was not influenced. No organic mercury species were detected after long-term application (>1 month) of mercury(II) chloride. The major mercury species was inorganic mercury(II) with substantial accumulation in the bacterial fraction (70%) and less in black sediment (21%) and ciliate fraction (9%) at the 25 micromol/L mercury(II) dose. The data indicate that free-living bacteria protect the ciliate cells by transforming mercury(II) into its insoluble forms.

Fructanolytic and saccharolytic enzymes of Treponema zioleckii strain kT.

Enzymes in the newly described rumen bacterium, Treponema zioleckii strain kT, capable of digesting Timothy grass fructan, inulin, and sucrose were identified and characterized. Two specific endolevanases and one non-specific beta-fructofuranosidase were found in a cell-free extract. The molecular weight of the endolevanases were estimated to be 60 and 36 kDa, whereas that of beta-fructofuranosidase, 87 kDa. The former of the specific enzymes was associated with the outer membrane, while the latter and the non-specific beta-fructofuranosidase, with the periplasm or cytosol. The K(m) and V(max) for Timothy grass fructan degradation by endolevanase were 0.27% and 15.75 microM fructose equivalents x mg protein(-1) x min(-1), those for sucrose and inulin digestion by beta-fructofuranosidase were 1.35 x 10(-3)M and 1.73 microM hexoses x mg protein(-1) x min(-1) and 1.77% and 1.83 microM hexoses x mg protein(-1) x min(-1), respectively.

Specific-heat study of the Ce(1 - x)Y(x)PdAl system.

We report on specific-heat measurements of the heavy-fermion compounds Ce(1 - x)Y(x)PdAl (0 ≤ x ≤ 1) between 0.35 and 300 K and in magnetic fields up to 14 T. Ce(1 - x)Y(x)PdAl compounds crystallize in the hexagonal ZrNiAl-type structure and CePdAl orders antiferromagnetically below T(N) = 2.8 K. The specific heat measured in external magnetic fields is also consistent with the antiferromagnetic order and the phase transition to the ferromagnetic state in fields around 4 T. The temperature dependence of the magnetic specific heat in CePdAl indicates magnetic correlations far above T(N). Substitution of nonmagnetic Y for magnetic Ce ions reduces T(N) rapidly and the antiferromagnetic order vanishes around x = 0.2. The Sommerfeld coefficient γ of the electronic specific heat is temperature dependent and increases strongly at low temperatures for all Ce concentrations.

Specific heat measurements and structural investigation of CeCu(6-x)Sn(x) compounds.

The evolution of the crystal structure and some magnetic properties of the heavy-fermion material CeCu(6-x)Sn(x) (x = 0, 0.25, 0.65, 0.75, 0.85 and 1.0) has been studied by powder neutron diffraction and by specific heat measurements. The substitution of Cu by Sn suppresses the temperature induced orthorhombic to monoclinic transition, known to occur in the pure CeCu(6) phase. No structural phase transition has been observed in these samples as a function of x but the cell volume increases considerably in an anisotropic way. Sn occupies preferentially the special Cu crystallographic site which is next to each of the four Ce atoms in the unit cell. The transition to antiferromagnetic order, characterizing the samples with higher x, is sensitive to both x and magnetic field. The results are discussed in the context of the competition between Kondo and RKKY interactions in disordered or not heavy-fermion systems and reveal an interesting interplay between composition, structure and magnetism in CeCu(6-x)Sn(x).

The another toxic effect of carbamate insecticides.

The activities of the antioxidant and detoxifying enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx), glutathione reductase (GR), glutathione-S-transferase (GST), and the content of thiobarbituric acid reactive substances (TBARS) were determined in the liver and kidney of rabbits after exposure to bendiocarb. In the liver, the activities of SOD, CAT and GR were not affected by bendiocarb. The induction or inhibition of isoenzymes of SOD (mainly MnSOD) were observed in the experimental groups. The activities of GSHPx-cum and GSHPx-H2O2 significantly decreased on the days 3 and 10 of the experiment. The activity of GST significantly increased on the day 9 of the experiment. In the kidney, the activity of SOD was significantly increased and the new MnSOD isoenzymes were detected. The activities of CAT and GSHPx-H2O2 were significantly decreased in the experimental groups. The activity of GR significantly increased on days 3 and 10, and the activity of GST was significantly increased on days 3, 10, and 30. Exposure of rabbit to bendiocarb did not affect the content of TBARS in the kidney. In the liver, the content of TBARS was significantly increased in the experimental groups as compared to the control. Our results showed that the response of organs to bendiocarb is different and may depend on the specific organ damage and their protective abilities. The alterations in the activities of the antioxidant defence system, increased TBARS values, and changes in the SOD isoenzyme pattern showed that the toxic effect of bendiocarb is not only in the acetylcholine esterase inhibition, but also in ROS production.

Sucrose phosphorylase of the rumen bacterium Pseudobutyrivibrio ruminis strain A.

AIMS: To verify the taxonomic affiliation of bacterium Butyrivibrio fibrisolvens strain A from our collection and to characterize its enzyme(s) responsible for digestion of sucrose. METHODS AND RESULTS: Comparison of the 16S rRNA gene of the bacterium with GenBank showed over 99% sequence identity to the species Pseudobutyrivibrio ruminis. Molecular filtration, native electrophoresis on polyacrylamide gel, zymography and thin layer chromatography were used to identify and characterize the relevant enzyme. An intracellular sucrose phosphorylase with an approximate molecular mass of 52 kDa exhibiting maximum activity at pH 6.0 and temperature 45 degrees C was identified. The enzyme was of inducible character and catalysed the reversible conversion of sucrose to fructose and glucose-1-P. The reaction required inorganic phosphate. The K(m) for glucose-1-P formation and fructose release were 3.88 x 10(-3) and 5.56 x 10(-3) mol l(-1) sucrose, respectively - while the V(max) of the reactions were -0.579 and 0.9 mumol mg protein(-1) min(-1). The enzyme also released free glucose from glucose phosphate. CONCLUSION: Pseudobutyrivibrio ruminis strain A utilized sucrose by phosphorolytic cleavage. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacterium P. ruminis strain A probably participates in the transfer of energy from dietetary sucrose to the host animal.

The alteration of glutathione peroxidase activity in rat organs after lead exposure.

The activity response of the antioxidant enzymes glutathione peroxidase (GPx), glutathione reductase (GR) and the contents of thiobarbituric reactive substances (TBARS) were investigated in rats exposed to lead. The enzyme activities were determined in the liver, kidney and heart of male and female rats which were received 100 mg and 1000 mg of lead acetate per liter water for 18 weeks. The statistical analyses indicated the differences related to the organs and to the sex of animals. Administration of lead evoked decrease of GPx activity in the kidney of both male and female rats. On the contrary, GPx activity increased in the heart of female rats, while in the male rats the higher dose of lead evoked a decrease in activity. In the kidneys of male rats and in the heart of female rats thiobarbituric acid reactive substances (TBARS), an indicators of oxidative stress, significantly increased in rats which were given the high lead dose. Most likely the observed changes could be a compensatory response to different lead accumulation in the male and female organs and also the possible distinct mechanisms in ROS elimination.