53 research outputs found
Complete high-quality genome sequence of Clostridium limosum (Hathewaya limosa) isolate 14S0207, recovered from a cow with suspected blackleg in Germany
Clostridium limosum can be found in soil and the intestinal tract of animals. In 2014, C. limosum was isolated from a suspected blackleg outbreak in cattle in Schleswig-Holstein, Germany. We present a complete genome sequence of a C. limosum strain represented by a circular chromosome and three plasmids
A Resonant soft x-ray powder diffraction study to determine the orbital ordering in A-site ordered SmBaMn2O6
Soft X-ray resonant powder diffraction has been performed at the Mn L2,3
edges of A-site ordered SmBaMn2O6. The energy and polarization dependence of
the (1/2 1/2 0) reflection provide direct evidence for a (x2-z2)/(y2-z2) type
orbital ordering in contrast to the single layer manganite. The temperature
dependence of the reflection indicates an orbital reorientation transition at
210 K, below which the charge and orbital ordered MnO2 sheets show AAAA type of
stacking. The concurring reduction of the ferromagnetic super exchange
correlations leads to further charge localization
Doping and temperature dependence of Mn 3d states in A-site ordered manganites
We present a systematic study of the electronic structure in A-site ordered
manganites as function of doping and temperature. The energy dependencies
observed with soft x-ray resonant diffraction (SXRD) at the Mn L_{2,3} edges
are compared with structural investigations using neutron powder diffraction as
well as with cluster calculations. The crystal structures obtained with neutron
powder diffraction reflect the various orbital and charge ordered phases and
show an increase of the Mn-O-Mn bond angle as function of doping and
temperature. Cluster calculations show that the observed spectral changes in
SXRD as a function of doping are more pronounced than expected from an increase
in bandwitdh due to the increase in Mn-O-Mn bond angle, and are best described
by holes that are distributed at the neighbouring oxygen ions. These holes are
not directly added to the Mn 3d shell, but centered at the Mn site. In
contrast, the spectral changes in SXRD as function of temperature are best
described by an increase of magnetic correlations. This demonstrates the strong
correlations between orbitals and magnetic moments of the 3d states
Circularly polarized resonant soft x-ray diffraction study of helical magnetism in hexaferrite
Magnetic spiral structures can exhibit ferroelectric moments as recently
demonstrated in various multiferroic materials. In such cases the helicity of
the magnetic spiral is directly correlated with the direction of the
ferroelectric moment and measurement of the helicity of magnetic structures is
of current interest. Soft x-ray resonant diffraction is particularly
advantageous because it combines element selectivity with a large magnetic
cross-section. We calculate the polarization dependence of the resonant
magnetic x-ray cross-section (electric dipole transition) for the basal plane
magnetic spiral in hexaferrite Ba0.8Sr1.2Zn2Fe12O22 and deduce its domain
population using circular polarized incident radiation. We demonstrate there is
a direct correlation between the diffracted radiation and the helicity of the
magnetic spiral.Comment: 4 pages, 4 figure
Magnetic and electronic Co states in layered cobaltate GdBaCo2O5.5-x
We have performed non-resonant x-ray diffraction, resonant soft and hard
x-ray magnetic diffraction, soft x-ray absorption and x-ray magnetic circular
dichroism measurements to clarify the electronic and magnetic states of the
Co3+ ions in GdBaCo2O5.5. Our data are consistent with a 3+ Py Co HS state at
the pyramidal sites and a 3+ Oc Co LS state at the octahedral sites. The
structural distortion, with a doubling of the a axis (2ap x 2ap x 2ap cell),
shows alternating elongations and contractions of the pyramids and indicates
that the metal-insulator transition is associated with orbital order in the t2g
orbitals of the 3+ Py Co HS state. This distortion corresponds to an
alternating ordering of xz and yz orbitals along the a and c axes for the 3+ Py
Co . The orbital ordering and pyramidal distortion lead to deformation of the
octahedra, but the 3+ Oc Co LS state does not allow an orbital order to occur
for the 3+ Oc Co ions. The soft x-ray magnetic diffraction results indicate
that the magnetic moments are aligned in the ab plane but are not parallel to
the crystallographic a or b axes. The orbital order and the doubling of the
magnetic unit cell along the c axis support a non-collinear magnetic structure.
The x-ray magnetic circular dichroism data indicate that there is a large
orbital magnetic contribution to the total ordered Co moment
Genome Sequence Analysis of Clostridium chauvoei Strains of European Origin and Evaluation of Typing Options for Outbreak Investigations
Black quarter caused by Clostridium (C.) chauvoei is an important bacterial disease that affects cattle and sheep with high mortality. A comparative genomics analysis of 64 C. chauvoei strains, most of European origin and a few of non-European and unknown origin, was performed. The pangenome analysis showed limited new gene acquisition for the species. The accessory genome involved prophages and genomic islands, with variations in gene composition observed in a few strains. This limited accessory genome may indicate that the species replicates only in the host or that an active CRISPR/Cas system provides immunity to foreign genetic elements. All strains contained a CRISPR type I-B system and it was confirmed that the unique spacer sequences therein can be used to differentiate strains. Homologous recombination events, which may have contributed to the evolution of this pathogen, were less frequent compared to other related species from the genus. Pangenome single nucleotide polymorphism (SNP) based phylogeny and clustering indicate diverse clusters related to geographical origin. Interestingly the identified SNPs were mostly non-synonymous. The study demonstrates the possibility of the existence of polymorphic populations in one host, based on strain variability observed for strains from the same animal and strains from different animals of one outbreak. The study also demonstrates that new outbreak strains are mostly related to earlier outbreak strains from the same farm/region. This indicates the last common ancestor strain from one farm can be crucial to understand the genetic changes and epidemiology occurring at farm level. Known virulence factors for the species were highly conserved among the strains. Genetic elements involved in Nicotinamide adenine dinucleotide (NAD) precursor synthesis (via nadA, nadB, and nadC metabolic pathway) which are known as potential anti-virulence loci are completely absent in C. chauvoei compared to the partial inactivation in C. septicum. A novel core-genome MLST based typing method was compared to sequence typing based on CRISPR spacers to evaluate the usefulness of the methods for outbreak investigations
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