Editors' Choice

Science  20 May 2016:
Vol. 352, Issue 6288, pp. 950
  1. Microbiota

    Bacteria fail to teach self-tolerance

    1. Kristen L. Mueller

    Components of the early microbiome in Finnish and Estonian children may impact autoimmunity risk.

    CREDIT: JONATHAN SMITH/ALAMY

    Differences in gut microbes, particularly early in life, are likely to contribute to a person's susceptibility to autoimmunity. Vatanen et al. explored this phenomenon by comparing the microbiomes of children from Finland, Estonia, and Russia from birth to 3 years old. Russians have lower incidences of autoimmunity than Finns and Estonians, and their microbiomes early in life differed, too, with Finnish and Estonian children harboring larger amounts of Bacteroides species. The primary source of bacterial lipopolysaccharide (LPS), an immunomodulatory molecule, also differed among the children. Bacteroides-derived LPS, which probably dominates in Finnish and Estonian children, did a poor job of teaching immune cells self-tolerance in cell culture and in mice, suggesting that it may contribute to autoimmune susceptibility in these populations.

    Cell 165, 842 (2016).

  2. Synthetic Biology

    Bacteria wired for pattern formation

    1. L. Bryan Ray

    Biological regulatory systems often have impressive adaptability that can, for example, ensure that large and small individuals have appropriately sized organs. This general property is called scale invariance and can result from the interpretation of morphogenetic gradients. Cao et al. show another way in which scale invariance can be achieved. Experiments with, and mathematical modeling of, a relatively simple synthetic genetic circuit implemented in a colony of bacteria produced a ring of fluorescently labeled cells that was proportional to the size of the colony of growing cells. The pattern is explained by restrictions imposed by feedback and feedforward loops in the circuit, and cues from the accumulation of an inhibitor or consumption of a nutrient that allow the colony to sense the size of the growth environment.

    Cell 10.1016/j.cell.2016.03.006 (2016).

  3. Electric Vehicles

    Life-cycle tradeoffs of plug-ins

    1. Nicholas S. Wigginton

    Roger Wallace in his electric car, 1899.

    PHOTO: © HERITAGE IMAGE PARTNERSHIP LTD / ALAMY STOCK PHOTO

    Shifting to electric passenger vehicles ideally will reduce the carbon footprint of the transportation sector. Two recent studies, however, show that the greenhouse gas emissions produced over the life cycle of electric vehicles, from production through use, may not always be less than those of gasoline-burning vehicles. Ellingsen et al. reveal that vehicle and battery size prohibit some larger electric vehicles from ever overcoming the high greenhouse gas emissions generated during production. Yuksel et al. show that regional factors in the United States such as electrical grid mix, temperature, and driving conditions strongly limit the potential of plug-in electric vehicles to out-perform high-efficiency gas vehicles. Blanket policies directed at the adoption of electric vehicles therefore could potentially fail to reduce the transportation sector's large carbon footprint.

    Environ. Res. Lett. 11, 054010, 044007 (2016).

  4. Biogeography

    Range limits and niche limits

    1. Andrew M. Sugden

    Do the geographical range limits of species reflect the limits of their ecological niches, or are they determined more by limits on their dispersal? These questions have long bothered ecologists, and they matter in the context of shifting distributions in a changing climate. Lee-Yaw et al. synthesized cases of 40 species (mainly plants) experimentally transplanted beyond their normal range limits, and they compared the results with niche models of habitat suitability. They found that for three-quarters of the species, range limits matched their niche limits, suggesting that most species are not dispersal-limited. The authors note, however, that dispersal limitation is likely to assume greater importance as habitats become increasingly fragmented by human activity.

    Ecol. Lett. 10.1111/ele.12604 (2016).

  5. Rock Mechanics

    Sliding into simulating slow slip

    1. Brent Grocholski

    A type of deformation on faults called slow slip releases similar amounts of energy as earthquakes, but without the familiar and frightening shaking. Leeman et al. use clever laboratory observations to investigate how faults might have a full range of behaviors ranging from slow slip to earthquake. They quantify the transition from silent to audible behavior in their simulated fault with a critical stiffness parameter, which depends on the frictional stability of the system. The result suggests that there exists a universal framework for understanding the range of slip behavior on natural faults.

    Nat. Commun. 10.1038/ncomms11104 (2016).

  6. Adaptation

    A genotype hitchhike along British railways

    1. Guy Riddihough

    Mutation allows plants to grow along herbicide treated railways.

    PHOTO: WIKIMEDIA COMMONS

    Triazine herbicides were widely used along British railways in the second half of the 20th century. A mutation in a chloroplast-encoded photosynthesis gene in the weed Arabidopsis thaliana confers resistance to the herbicide. Flood et al. show that resistant A. thaliana plants are found exclusively beside railway tracks. The resistance mutation in the chloroplast genome is associated with a single nuclear haplotype. This “genetic hitchhiking” of the whole nuclear genome probably results from the intense herbicide selection and high levels of inbreeding in A. thaliana. Thus, anthropogenic-driven selection can play a significant role in genome evolution.

    Curr. Biol., 10.1016/j.cub.2016.03.027 (2016).

  7. Education Policy

    Being selective does not pay off

    1. Brad Wible

    What you study, not where you study it, has the most impact on subsequent earnings—at least in Norway. Kirkeboen et al. studied the centralized postsecondary admissions system there and found that pursuit of a career in science instead of humanities almost tripled early career earnings, but attending a more selective school offered no advantage. This work has implications for explaining causes and consequences of postsecondary education choices. Consideration of alternative preferences and payoffs, and how shifting students from one field to another can ripple throughout the system, can inform policies aimed at expanding or contracting fields, as proposed by the U.S. President's Council of Advisors on Science and Technology.

    Quart. J. Econ. 10.1093/qje/qjw019 (2016).

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