Editors' Choice

Science  04 Mar 2016:
Vol. 351, Issue 6277, pp. 1039
  1. Plastic Pollution

    Earthworms on a microplastics diet

    1. Julia Fahrenkamp-Uppenbrink

    A common type of earthworm, Lumbricus terrestris

    PHOTO:© NATURE PICTURE LIBRARY/ALAMY STOCK PHOTO

    Microplastics commonly found in marine environments can cause harm to marine organisms when ingested. Terrestrial environments are also widely polluted with plastics, but little is known about their effect on terrestrial species. Huerta Lwanga et al. have investigated the effect of polyethylene microplastics in plant litter on earthworms. To provide a realistic exposure scenario, the authors added the microplastics to plant litter deposited on the soil surface. They show that environmentally relevant microplastic concentrations led to reduced earthworm growth and elevated mortality as compared to a control. Futhermore, earthworms may transport microplastics into soils, from which they may leach into surface waters.

    Environ. Sci. Technol. 10.1021/acs.est.5b05478 (2016).

  2. Microbiota

    For health, microbial location matters

    1. Kristen L. Mueller

    The composition of our gut microbes probably affects our health. For instance, certain microbes may predispose individuals to some types of cancer, alter their metabolism, or even contribute to the aging process. In flies, an altered microbial composition in the gastrointestinal (GI) tract can reduce life span. Li et al. investigated this further and found that the GI tract of younger flies compartmentalizes its resident microbes. As flies age, however, inflammatory signaling causes changes in the cells lining the GI tract, reducing its ability to maintain such compartmentalization. Blocking this process extends the life span of flies, suggesting that as for many things in life, location is key.

    Cell Host Microbe 19, 240 (2016).

  3. Trophic Cascades

    Innocent until proven guilty

    1. Sacha Vignieri

    Cownose rays may have been mistakenly implicated in bivalve decline

    PHOTO: © AURORA PHOTOS/ALAMY STOCK PHOTO

    The existence of trophic cascades is well documented; however, characterizing such linkages is more challenging than it might appear. Grubbs et al. reanalyzed data used to support the existence of a predator-mediated cascade from sharks, to cownose rays, to bivalves in the Atlantic and argue that the original connections need to be reexamined. Specifically, they found little evidence that the ray could biologically fit the role of damaging mesopredator in this system. Since the original study was conducted, the cownose ray has been the focus of unregulated fishing pressure justified, in part, as a way to protect the commercial bivalve industry. Such unregulated pressure could have detrimental effects on the very slowly reproducing rays, and draws attention away from other human contributions to bivalve decline.

    Sci. Rep. 10.1038/srep20970 (2016).

  4. Paleoanthropology

    Modeling Neandertal extinction

    1. Andrew M. Sugden

    The extinction of Neandertals in Europe is commonly thought to have been the result of competition with modern humans. Gilpin et al. test this possibility mathematically, with a model that explores the interaction between the level of cultural development and population size. The model confirms that differences in cultural level can lead to competitive exclusion of a larger population by a smaller one. An advantage in learning ability, for example, would ensure that modern humans replaced Neandertals, even though the initial discrepancy in population size was large. Although the reality of the Neandertal demise is likely to have been more complex (for example, there may have been cultural exchange between Neandertals and modern humans as well as competition), these models affirm the likelihood that cultural sophistication held sway.

    Proc. Natl Acad. Sci. U.S.A. 10.1073/pnas.1524861113 (2016).

  5. Oncogene Signaling

    KRAS gets the silencing treatment

    1. Paula A. Kiberstis

    Mutations in the KRAS protooncogene drive the growth of some of the most lethal human tumors, including pancreatic and lung cancers. Efforts to pharmacologically inhibit KRAS itself, or components of its well-studied signaling pathway, have been largely unsuccessful. Shankar et al. considered the possibility that KRAS may have additional uncharacterized roles that contribute to tumor development and that may be more susceptible to drug treatment. They explored this idea by using a sensitive method to identify new KRAS-binding proteins. One surprising hit was Argonaute 2 (AGO2), a protein required for RNA-mediated gene silencing. KRAS and AGO2 colocalize in the endoplasmic reticulum and their interaction alters the activity of each protein. Notably, AGO2 appears to enhance the transforming ability of KRAS in cultured cells.

    Cell Rep. 14, 1 (2016).

  6. Geophysics

    Forecasting cascading fault rupture

    1. Brent Grocholski

    Earthquake rupture forecasts provide vital estimates of the likelihood of future earthquakes in a region. However, Nissen et al. show that rupture forecasts can be muddied by not considering cascading multiple-fault ruptures. A combined geodetic and seismological reanalysis of a 1997 earthquake in Pakistan revealed dynamic triggering of a second fault 50 km away shortly after the first rupture. Current forecasts assume that triggering is limited to faults within 5 km. This observation suggests that longer-range, multiple-fault ruptures should be incorporated into forecasts, and it highlights the dangers resulting from this type of earthquake doublet.

    Nat. Geosci. 10.1038/ngeo2653 (2016).

  7. Solar Cell Materials

    Dropping lead from perovskites

    1. Phil Szuromi

    Although lead-based inorganic-organic perovskite solar cells can have efficiencies of up to ~20%, degradation of these materials during use can create water-soluble byproducts that could potentially release toxic lead ions into the environment. Slavney et al. report on an inorganic bismuth-based “double perovskite” (one in which the B and B′ sites alternate in the lattice) that has an indirect band gap of 1.95 electron volts, which is suitable for use as a tandem layer over a silicon solar cell. The material, Cs2AgBiBr6, is highly stable against heat and moisture and shows a photoluminescent lifetime of 600 ns, which suggests that carrier lifetimes may be long enough to achieve high efficiency.

    J. Am. Chem. Soc. 10.1021/jacs.5b13294 (2016).

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