Genomic variations associated with attenuation in Mycobacterium avium subsp paratuberculosis vaccine strains

BACKGROUND: Mycobacterium avium subspecies paratuberculosis (MAP) whole cell vaccines have been widely used tools in the control of Johne's disease in animals despite being unable to provide complete protection. Current vaccine strains derive from stocks created many decades ago; however their genotypes, underlying mechanisms and relative degree of their attenuation are largely unknown. RESULTS: Using mouse virulence studies we confirm that MAP vaccine strains 316 F, II and 2e have diverse but clearly attenuated survival and persistence characteristics compared with wild type strains. Using a pan genomic microarray we characterise the genomic variations in a panel of vaccine strains sourced from stocks spanning over 40 years of maintenance. We describe multiple genomic variations specific for individual vaccine stocks in both deletion (26-32 Kbp) and tandem duplicated (11-40 Kbp) large variable genomic islands and insertion sequence copy numbers. We show individual differences suitable for diagnostic differentiation between vaccine and wild type genotypes and provide evidence for functionality of some of the deleted MAP-specific genes and their possible relation to attenuation. CONCLUSIONS: This study shows how culture environments have influenced MAP genome diversity resulting in large tandem genomic duplications, deletions and transposable element activity. In combination with classical selective systematic subculture this has led to fixation of specific MAP genomic alterations in some vaccine strain lineages which link the resulting attenuated phenotypes with deficiencies in high reactive oxygen species handling

Crystal growth and magnetic structure of MnBi2Te4

Millimeter-sized MnBi$_2$Te$_4$ single crystals are grown out of Bi-Te flux and characterized by measuring magnetic and transport properties, scanning tunneling microscope (STM) and spectroscopy (STS). The magnetic structure of MnBi$_2$Te$_4$ below T$_N$ is determined by powder and single crystal neutron diffraction measurements. Below T$_N$=24\,K, Mn$^{2+}$ moments order ferromagnetically in the \textit{ab} plane but antiferromagnetically along the crystallographic \textit{c} axis. The ordered moment is 4.04(13) $\mu_{B}$/Mn at 10\,K and aligned along the crystallographic \textit{c}-axis. The electrical resistivity drops upon cooling across T$_N$ or when going across the metamagnetic transition in increasing fields below T$_N$. A critical scattering effect was observed in the vicinity of T$_N$ in the temperature dependence of thermal conductivity. However, A linear temperature dependence was observed for thermopower in the temperature range 2K-300K without any anomaly around T$_N$. These indicate that the magnetic order in Mn-Te layer has negligible effect on the electronic band structure, which makes possible the realization of proposed topological properties in MnBi$_2$Te$_4$ after fine tuning of the electronic band structure

Coupling Between An Optical Phonon and the Kondo Effect

We explore the ultra-fast optical response of Yb_{14}MnSb_{11}, providing further evidence that this Zintl compound is the first ferromagnetic, under-screened Kondo lattice. These experiments also provide the first demonstration of coupling between an optical phonon mode and the Kondo effect.Comment: 4 Pages, 3 Figures, submitted to Phys. Rev. Let

Female mice respond to male ultrasonic ‘songs’ with approach behaviour

The ultrasonic vocalizations of mice are attracting increasing attention, because they have been recognized as an informative readout in genetically modified strains. In addition, the observation that male mice produce elaborate sequences of ultrasonic vocalizations (‘song’) when exposed to female mice or their scents has sparked a debate as to whether these sounds are—in terms of their structure and function—analogous to bird song. We conducted playback experiments with cycling female mice to explore the function of male mouse songs. Using a place preference design, we show that these vocalizations elicited approach behaviour in females. In contrast, the playback of pup isolation calls or whistle-like artificial control sounds did not evoke approach responses. Surprisingly, the females also did not respond to pup isolation calls. In addition, female responses did not vary in relation to reproductive cycle, i.e. whether they were in oestrus or not. Furthermore, our data revealed a rapid habituation of subjects to the experimental situation, which stands in stark contrast to other species' responses to courtship vocalizations. Nevertheless, our results clearly demonstrate that male mouse songs elicit females' interest

Low thermal conductivity of the layered oxide (Na,Ca)Co_2O_4: Another example of a phonon glass and an electron crystal

The thermal conductivity of polycrystalline samples of (Na,Ca)Co_2O_4 is found to be unusually low, 20 mW/cmK at 280 K. On the assumption of the Wiedemann-Franz law, the lattice thermal conductivity is estimated to be 18 mW/cmK at 280 K, and it does not change appreciably with the substitution of Ca for Na. A quantitative analysis has revealed that the phonon mean free path is comparable with the lattice parameters, where the point-defect scattering plays an important role. Electronically the same samples show a metallic conduction down to 4.2 K, which strongly suggests that NaCo_2O_4 exhibits a glass-like poor thermal conduction together with a metal-like good electrical conduction. The present study further suggests that a strongly correlated system with layered structure can act as a material of a phonon glass and an electron crystal.Comment: 5 pages 3 figures, to be published in Phys. Rev.

Low-lying optical phonon modes in the filled skutterudite CeRu4Sb12

The phonon dynamics of filled skutterudite CeRu4Sb12 have been studied at room temperature by inelastic neutron scattering. Optical phonons associated with a large vibration of Ce atoms are observed at a relatively low energy of E = 6 meV, and show anticrossing behavior with acoustic phonons. We propose that the origin of the low lattice thermal conductivity in filled skutterudites can be attributed to intensive Umklapp scattering originating from low-lying optical phonons. By an analysis based on a Born-von Karman force model, the longitudinal force constants of the nearest Ce-Sb and Ce-Ru pairs are estimated to be 0.025 mdyn/A, while that of the nearest Ru-Sb pair is estimated to be 1.4 mdyn/A, indicating that the Ce atoms are bound very weakly to the surrounding rigid RuSb6-octahedron cages.Comment: 4pages, 5 figures, J. Phys. Soc. Jpn. (2006) in pres

Comparisons of reproductive function and fatty acid fillet quality between triploid and diploid farm Atlantic salmon (Salmo salar)

Triploidy could prevent escaped farm salmon breeding in the wild, while also improving nutrient quality within farmed fillets. Despite these potential advantages, triploid Atlantic salmon have not been widely used in aquaculture, and their reproductive function has yet to be fully evaluated. Here, we compare reproductive function and fillet composition between triploid and diploid farm salmon under standard aquaculture rearing conditions. We show that female triploids are sterile and do not develop gonads. By contrast, males produce large numbers of motile spermatozoa capable of fertilizing wild salmon eggs. However, compared with diploids, reproductive development and survival rates of eggs fertilized by triploid males were significantly reduced, with less than 1% of eggs sired by triploid males reaching late-eyed stages of development. Analyses of fillets showed that total lipid and fatty acid quantities were significantly lower in triploid than in diploid Atlantic salmon fillets. However, when fatty acids were normalized to total lipid content, triploid fillets had significantly higher relative levels of important omega-3 long-chain polyunsaturated fatty acids. Our results show that: (i) escaped triploid farm salmon are very unlikely to reproduce in the wild and (ii) if able to match diploid fillet lipid content, triploid farm salmon could achieve better fillet quality in terms of essential fatty acids

Effect of annealing on the specific heat of optimally doped Ba(Fe0.92_{0.92}Co0.08_{0.08})2_{2}As2_{2}

We report the temperature dependence of the low-temperature specific heat down to 400 mK of the electron-doped Ba(Fe$_{0.92}$Co$_{0.08}$)$_{2}$As$_{2}$ superconductors. We have measured two samples extracted from the same batch: first sample has been measured just after preparation with no additional heat treatment. The sample shows $T_{c}$=20 K, residual specific heat $\gamma_{0}$=3.6 mJ/mol K$^{2}$ and a Schottky-like contribution at low temperatures. A second sample has been annealed at 800 $^{o}C$ for two weeks and shows $T_{c}$ = 25 K and $\gamma_{0}$=1.4 mJ/mol~K$^{2}$. By subtracting the lattice specific heat, from pure BaFe$_{2}$As$_{2}$, the temperature dependence of the electronic specific heat has been obtained and studied. For both samples the temperature dependence of $C_{el}(T)$ clearly indicate the presence of low-energy excitations in the system. Their specific heat data cannot be described by single clean s- or d-wave models and the data requires an anisotropic gap scenario which may or may not have nodesComment: SCES 2010, 5 pages, 2 figure