Editors' Choice

Science  20 Jul 2018:
Vol. 361, Issue 6399, pp. 241
  1. Microbial Ecology

    Hack fracking for more methane

    1. Michael A. Funk

    Microbes increase methane output from shale gas wells.

    CREDIT: NAMTHIP MUANTHONGTHAE/SHUTTERSTOCK

    Microbes are thought to contribute to chemical processes that occur during hydraulic fracturing of shale. How these communities develop after injection of fracking fluid likely determines whether they are beneficial or detrimental. Borton et al. created laboratory models of the gas-well microbial community seeded with fluid from an active well. Microbes that might boost the methane output of wells proliferated in test conditions amended with glycine betaine, a metabolite produced to counteract the salinity of the well fluids. Amino acid fermentation reactions provided an energy source for the dominant microbes in the culture. The authors analyzed well fluid from 41 active wells in the eastern United States and confirmed production of metabolites that was consistent with the metabolic pathways identified in the laboratory.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1800155115 (2018).

  2. Neurodevelopment

    Was Voldemort losing Robo signaling?

    1. Pamela J. Hines

    Primates have larger and more complex brains than those of reptiles. The cortices of reptile and bird brains are formed through direct neurogenesis, as radial glia divide to generate neurons. In primates, on the other hand, an amplification step is thrown in with the intermediate progenitors that results in more neurons. Cárdenas et al. look at the patterns and regulators of neurogenesis in snake, chicken, mouse, and human brain organoids. Experimental manipulations that directed more signaling from Roundabout (Robo) transmembrane receptors and less from the Notch ligand Dll1 caused human brain organoids to lose indirect neurogenesis, whereas less Robo and more Dll1 caused snake embryos to gain indirect neurogenesis. Thus, shifts in Robo and Dll expression during evolution may have tilted the balance of direct and indirect neurogenesis. The indirect neurogenesis characteristic of primate brain development may be a slower way to build a brain, but the resulting brain has a lot more neurons than a snake's does.

    Cell 10.1016/j.cell.2018.06.007 (2018).

  3. Neuroscience

    Different species solve problems differently

    1. Peter Stern

    Tree shrews (like this one) and long-tailed macaques perform differently than rats on a vision-based test.

    PHOTO: NEIL BOWMAN/MINDEN PICTURES

    The most powerful methods available for investigating the neural correlates of perceptual learning increasingly rely on rodents as animal models. The implicit assumption is that whenever rodents perform a task, they engage a similar neural circuitry as other species, such as primates. This is problematic for visual system studies because rodent vision is poor. Mustafar et al. examined the behavior of rats, long-tailed macaques, and tree shrews as they learned an identical visual discrimination task. Rats learned more slowly and had a lower peak performance than the other species. They also learned in a different way: Throughout training, including after acquisition, rats used reward history to guide their performance, unlike long-tailed macaques and tree shrews. These results indicate the necessity of careful comparative studies in translational research.

    eNeuro 10.1523/ENEURO.0167-18.2018 (2018).

  4. Metabolism

    Metabolic changes in gut surgery

    1. Ming Yang

    Roux-en-Y gastric bypass surgery (RYGB) is an effective treatment strategy for obesity. Whether RYGB-mediated weight loss is directly associated with the long-term metabolic benefits remains elusive. Ben-Zvi et al. studied the physiological adaptations of obese mice subjected to RYGB or calorie restriction and compared the results with data for post-RYGB patients. RYGB-operated mice displayed beiging of adipose tissue and short-term skeletal muscle adaptations not observed in calorie-restricted mice. Meanwhile, altered amino acid metabolism in the liver and intestinal immune and metabolic changes were conserved between RYGB-operated mice and humans. These integrated organ adaptations exhibited a time-dependent pattern of activation coordinated with the circadian clock network, providing evidence that metabolic changes associated with RYGB are not attributable to weight loss alone.

    Cell Metab. 10.1016/j.cmet.2018.06.004 (2018).

  5. DNA Methylation

    Differential methylation affects risk of MS

    1. Laura M. Zahn

    Specific variants of the human leukocyte antigen (HLA) locus are heritable risk factors for the autoimmune disease multiple sclerosis (MS). However, how these variants confer risk is not well understood. It has been proposed that epigenetic modifications, such as differences in methylation, of noncoding regions near the HLA coding regions may explain why some people are more likely to develop MS. Comparing controls and patients, Kular et al. identified hypomethylated genomic regions associated with increases in gene expression at the HLA locus that increased the risk of developing MS. Extending this investigation, the authors identified a protective variant that reduces the probability of developing MS that is more highly methylated.

    Nat. Commun. 10.1038/s41467-018-04732-5 (2018).

  6. Physics

    A fluid of tiny magnets

    1. Jelena Stajic

    One of the most fascinating phenomena in many-body systems is the emergence of so-called collective modes, where the constituents of the system start acting in sync. Lepoutre et al. revealed such behavior in an ultracold gas of chromium atoms, which carry a large magnetic moment. The researchers first coaxed the atoms' spins to align along a direction perpendicular to an external magnetic field, which had a small gradient. The gradient acted to couple the atoms' spin and spatial degrees of freedom, resulting in a collective mode in which the spins oscillated with an amplitude that was dependent on their position. The experimental results were consistent with a hydrodynamic model.

    Phys. Rev. Lett. 121, 013201 (2018).

  7. Inorganic Chemistry

    Noble xenon wears a crown

    1. Jake Yeston

    Nobility has its privileges. In chemistry, it means, comparatively speaking, being left alone. The noble gases react with very few other substances, although xenon in particular can bond to fluorine or oxygen before pushing them away—sometimes violently—to more receptive elements. Marczenko et al. now report that xenon can also wear a crown: more specifically a crown ether. As verified by x-ray crystallography, the crown clings electrostatically to XeO3 through five coordinated oxygens and diminishes the latter's shock sensitivity.

    Angew. Chem. Int. Ed. 10.1002/anie.201806640 (2018).