A Genetic Strategy for Probing the Functional Diversity of Magnetosome Formation

Model genetic systems are invaluable, but limit us to understanding only a few organisms in detail, missing the variations in biological processes that are performed by related organisms. One such diverse process is the formation of magnetosome organelles by magnetotactic bacteria. Studies of model magnetotactic α-proteobacteria have demonstrated that magnetosomes are cubo-octahedral magnetite crystals that are synthesized within pre-existing membrane compartments derived from the inner membrane and orchestrated by a specific set of genes encoded within a genomic island. However, this model cannot explain all magnetosome formation, which is phenotypically and genetically diverse. For example, Desulfovibrio magneticus RS-1, a δ-proteobacterium for which we lack genetic tools, produces tooth-shaped magnetite crystals that may or may not be encased by a membrane with a magnetosome gene island that diverges significantly from those of the α-proteobacteria. To probe the functional diversity of magnetosome formation, we used modern sequencing technology to identify hits in RS-1 mutated with UV or chemical mutagens. We isolated and characterized mutant alleles of 10 magnetosome genes in RS-1, 7 of which are not found in the α-proteobacterial models. These findings have implications for our understanding of magnetosome formation in general and demonstrate the feasibility of applying a modern genetic approach to an organism for which classic genetic tools are not available

Dressed-State Resonant Coupling between Bright and Dark Spins in Diamond

Under ambient conditions, spin impurities in solid-state systems are found in thermally mixed states and are optically “dark”; i.e., the spin states cannot be optically controlled. Nitrogen-vacancy (NV) centers in diamond are an exception in that the electronic spin states are “bright”; i.e., they can be polarized by optical pumping, coherently manipulated with spin-resonance techniques, and read out optically, all at room temperature. Here we demonstrate a scheme to resonantly couple bright NV electronic spins to dark substitutional-nitrogen (P1) electronic spins by dressing their spin states with oscillating magnetic fields. This resonant coupling mechanism can be used to transfer spin polarization from NV spins to nearby dark spins and could be used to cool a mesoscopic bath of dark spins to near-zero temperature, thus providing a resource for quantum information and sensing, and aiding studies of quantum effects in many-body spin systems.Engineering and Applied SciencesPhysic

Magnetic field imaging with nitrogen-vacancy ensembles

Part of Focus on Diamond-Based Photonics and Spintronics We demonstrate a method of imaging spatially varying magnetic fields using a thin layer of nitrogen-vacancy (NV) centers at the surface of a diamond chip. Fluorescence emitted by the two-dimensional NV ensemble is detected by a CCD array, from which a vector magnetic field pattern is reconstructed. As a demonstration, ac current is passed through wires placed on the diamond chip surface, and the resulting ac magnetic field patterns are imaged using an echo-based technique with sub-micron resolution over a 140 μm×140 μm field of view, giving single-pixel sensitivity \sim100\,{\rm nT}/\sqrt{{\rm Hz}} . We discuss ongoing efforts to further improve the sensitivity, as well as potential bioimaging applications such as real-time imaging of activity in functional, cultured networks of neurons. PACS 61.72.J- Point defects and defect clusters 78.55.Hx Other solid inorganic materials 87.50.C- Static and low-frequency electric and magnetic fields effects 85.30.Tv Field effect devices Subjects Electronics and devices Condensed matter: electrical, magnetic and optical Semiconductors Medical physics Biological physics Condensed matter: structural, mechanical & thermalUnited States. Defense Advanced Research Projects AgencyNational Institute of Standards and Technology (U.S.)National Science Foundation (U.S.

Paleomagnetism. Solar nebula magnetic fields recorded in the Semarkona meteorite.

Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constraints on the intensity of these fields. Here we show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54 ± 21 microteslas. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the Sun. This implies that background magnetic fields in the terrestrial planet-forming region were likely 5 to 54 microteslas, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.This is the accepted manuscript. The final version is available from Science at http://www.sciencemag.org/content/346/6213/1089.abstract

Synthetic lethality between PAXX and XLF in mammalian development.

PAXX was identified recently as a novel nonhomologous end-joining DNA repair factor in human cells. To characterize its physiological roles, we generated Paxx-deficient mice. Like Xlf-/- mice, Paxx-/- mice are viable, grow normally, and are fertile but show mild radiosensitivity. Strikingly, while Paxx loss is epistatic with Ku80, Lig4, and Atm deficiency, Paxx/Xlf double-knockout mice display embryonic lethality associated with genomic instability, cell death in the central nervous system, and an almost complete block in lymphogenesis, phenotypes that closely resemble those of Xrcc4-/- and Lig4-/- mice. Thus, combined loss of Paxx and Xlf is synthetic-lethal in mammals.Research in S.P.J.’s laboratory is funded by Cancer Research UK (CRUK) program grant number C6/A11224, the European Research Council, and the European Community Seventh Framework Programme grant agreement number HEALTH-F2-2010-259893 (DDResponse). Core funding is provided by CRUK (C6946/A14492) and the Wellcome Trust (WT092096). S.P.J. receives his salary from the University of Cambridge, UK, supplemented by CRUK. L.D.’s laboratory is funded by the Institut Pasteur as well as the European Research Council (ERC) under starting grant agreement number 310917. D.J.A.’s laboratory is supported by CRUK and the Wellcome Trust. A.N.B. is supported by a CRUK Career Development Fellowship (C29215/A20772).This is the final version of the article. It first appeared from Cold Spring Harbor Laboratory Press via https://doi.org/10.1101/gad.290510.11

Quasar induced galaxy formation: a new paradigm ?

We discuss observational evidence that quasars play a key role in the formation of galaxies starting from the detailed study of the quasar HE0450-2958 and extending the discussion to a series of converging evidence that radio jets may trigger galaxy formation. The direct detection with VISIR at the ESO-VLT of the 7 kpc distant companion galaxy of HE0450-2958 allows us to spatially separate the sites of quasar and star formation activity in this composite system made of two ultra-luminous infrared galaxies (ULIRGs). No host galaxy has yet been detected for this quasar, but the companion galaxy stellar mass would bring HE0450-2958 in the local M(BH)-M(stellar bulge) relation if it were to merge with the QSO. This is bound to happen because of their close distance (7 kpc) and small relative velocity (~60-200 km/s). We conclude that we may be witnessing the building of the M(BH)-M(stellar bulge) relation, or at least of a major event in that process. The star formation rate (~340 Msun/yr), age (40-200 Myr) and stellar mass ([5-6]x10^10 Msun) are consistent with jet-induced formation of the companion galaxy. We suggest that HE0450-2958 may be fueled in fresh material by cold gas accretion from intergalactic filaments. We map the projected galaxy density surrounding the QSO as a potential tracer of intergalactic filaments and discuss a putative detection. Comparison to other systems suggests that inside-out formation of quasar host galaxies and jet-induced galaxy formation may be a common process. Two tests are proposed for this new paradigm: (1) the detection of offset molecular gas or dust emission with respect to the position of distant QSOs, (2) the delayed formation of host galaxies as a result of QSO activity, hence the two step building of the M(BH)/M(stellar bulge) ratio.Comment: 15 pages, 8 figures, accepted for publication in Astronomy and Astrophysics (with minor corrections

A core outcome set for aphasia treatment research: the ROMA consensus statement

Background: A core outcome set (COS; an agreed, minimum set of outcomes) was needed to address the heterogeneous measurement of outcomes in aphasia treatment research and to facilitate the production of transparent, meaningful and efficient outcome data. Objective: The Research Outcome Measurement in Aphasia (ROMA) consensus statement provides evidence-based recommendations for the measurement of outcomes for adults with post-stroke aphasia within phase I-IV aphasia treatment studies. Methods: This statement was informed by a four-year program of research which comprised investigation of stakeholder-important outcomes using consensus processes, a scoping review of aphasia outcome measurement instruments, and an international consensus meeting. This paper provides an overview of this process and presents the results and recommendations arising from the international consensus meeting. Results: Five essential outcome constructs were identified: Language, communication, patient-reported satisfaction with treatment and impact of treatment, emotional wellbeing, and quality of life. Consensus was reached for the following measurement instruments: Language: The Western Aphasia Battery Revised (WAB-R) (74% consensus); emotional well-being: General Health Questionnaire (GHQ)-12 (83% consensus); quality of life: Stroke and Aphasia Quality of Life Scale (SAQOL-39) (96% consensus). Consensus was unable to be reached for measures of communication (where multiple measures exist) or patient-reported satisfaction with treatment or impact of treatment (where no measures exist). Discussion: Harmonisation of the ROMA COS with other core outcome initiatives in stroke rehabilitation is discussed. Ongoing research and consensus processes are outlined. Conclusion: The WAB-R, GHQ, and SAQOL-39 are recommended to be routinely included within phase I-IV aphasia treatment studies. This consensus statement has been endorsed by the Collaboration of Aphasia Trialists, the British Aphasiology Society, the German Society for Aphasia Research and Therapy, and the Royal College of Speech Language Therapists

The American Congress of Rehabilitation Medicine Diagnostic Criteria for Mild Traumatic Brain Injury

Objective: To develop new diagnostic criteria for mild traumatic brain injury (TBI) that are appropriate for use across the lifespan and in sports, civilian trauma, and military settings. Design: Rapid evidence reviews on 12 clinical questions and Delphi method for expert consensus. Participants: The Mild Traumatic Brain Injury Task Force of the American Congress of Rehabilitation Medicine Brain Injury Special Interest Group convened a Working Group of 17 members and an external interdisciplinary expert panel of 32 clinician-scientists. Public stakeholder feedback was analyzed from 68 individuals and 23 organizations. Results: The first 2 Delphi votes asked the expert panel to rate their agreement with both the diagnostic criteria for mild TBI and the supporting evidence statements. In the first round, 10 of 12 evidence statements reached consensus agreement. Revised evidence statements underwent a second round of expert panel voting, where consensus was achieved for all. For the diagnostic criteria, the final agreement rate, after the third vote, was 90.7%. Public stakeholder feedback was incorporated into the diagnostic criteria revision prior to the third expert panel vote. A terminology question was added to the third round of Delphi voting, where 30 of 32 (93.8%) expert panel members agreed that ‘the diagnostic label ‘concussion’ may be used interchangeably with ‘mild TBI’ when neuroimaging is normal or not clinically indicated.’ Conclusions: New diagnostic criteria for mild TBI were developed through an evidence review and expert consensus process. Having unified diagnostic criteria for mild TBI can improve the quality and consistency of mild TBI research and clinical care.</p