Editors' Choice

Science  22 Dec 2017:
Vol. 358, Issue 6370, pp. 1552
  1. Sexual Signaling

    Choosing to amplify

    1. Sacha Vignieri

    Tree crickets can create nearly perfect acoustic baffles to amplify their calls.

    PHOTO: NATASHA MHATRE

    Crickets are well known for the calls that the males make to attract females. Just listening to a cricket chorus, however, emphasizes the challenge that these little insects have to be heard above the din. Tree crickets (Oecanthus henryi) have evolved the ability to use leaves as a baffle to amplify their calls, but not all males use these baffles, and in some years, only a rare few do so. Mhatre et al. found that when males chose to amplify, they selected the best-sized leaf available and optimized it to create a nearly perfect baffle. The fact that they only rarely chose to do so suggests that there may be a cost to such baffle creation. Further, although the authors did not determine whether baffling allows high-quality males to better advertise or lower-quality males to fib, they argue that opting to baffle (or not) involves an inherited, yet behaviorally intensive, set of choices.

    eLife 10.7554/eLife.32763 (2017).

  2. Infection

    Aiding and abetting Staphylococcus aureus

    1. Caroline Ash

    Human skin hosts an ecosystem of microorganisms. Infections can therefore involve more than one organism, but antibiotic therapy options rarely consider the possibility of interference by a nontarget species. Staphylococcus aureus is a member of the normal skin microbiota that can show a spectrum of virulence and cause persistent and intractable infections. Radlinski et al. show that co-infections of S. aureus and Pseudomonas aeruginosa can synergize in multiple ways to antagonize or potentiate antibiotic susceptibility in S. aureus. P. aeruginosa secretes a series of secondary products in a strain-specific manner. Some, such as rhamnolipids or LasA endopeptidase, increase S. aureus susceptibility to antibiotics. Others, such as HQNO, induce multidrug tolerance and potentiate antibiotic resistance in S. aureus. Some of these interactions could theoretically be exploited to assist treatment, but the reciprocal effects of S. aureus on P. aeruginosa, coupled with strain variation, mean each case is different.

    PLOS Biol. 10.1371/journal.pbio.2003981 (2017).

  3. Cell Reprogramming

    Cell mechanics indicate cell fate

    1. Beverly A. Purnell

    Gene expression changes are accompanied by biophysical phenotypes during differentiation or reprogramming, as has now been shown by measurements of cell stiffness or relative compliancy. Using real-time deformability cytometry (a microfluidic-based method that deforms cells by stress) and atomic force microscopy-enabled nanoindentation, Urbanska et al. characterized mouse fetal neural progenitor cells (fNPCs) that are induced to become pluripotent stem cells (iPSCs) through the introduction of four transcription factors and subsequently differentiate toward the neural lineage. As differentiated cells are reprogrammed to a pluripotent state, they become stiffer, but in the reverse path, pluripotent cells become more compliant as they differentiate. iPSC stiffness is similar to that of embryonic stem cells. These mechanical properties may serve as biophysical markers for pluripotency.

    Development 10.1242/dev.155218 (2017).

  4. Optics

    Optimizing optical antennae

    1. Ian S. Osborne

    Nanophotonic technology relies on the ability to capture freely propagating light and convert it to a nanometer-scale plasmonic excitation on a chip. Optical antennae are devices that can be used in that capacity but so far are suboptimal for such applications. Feichtner et al. attribute their poor performance to the fact that present antenna designs are based on larger-scale radiowave rules, which fail to capture the light-matter interaction in sufficient detail. By taking into account the optical properties of materials at the nanometer scale, the authors present an enhanced theoretical description for optical antenna design that should result in high-performance structures that optimize the coupling between a quantum emitter and the antenna.

    Phys. Rev. Lett. 119, 217401 (2017).

  5. Ice Sheets

    Melting around the margins

    1. H. Jesse Smith

    A Landsat 8 satellite image of the Helheim-Sermilik glacier-fjord system in summer

    CREDIT: T. MOON ET AL., NAT. GEOSCI. 10.1038/S41561-017-0018-Z (2017)

    How and when is fresh water added to the margins of ice sheets? That question is central to understanding the effects of ice sheet melting on ocean water properties, circulation, and biological systems, on scales from local to basinwide. Moon et al. used an innovative observational and modeling method to produce a freshwater flux budget for the Helheim-Sermilik glacier-fjord system in Greenland. They determine that iceberg melt is the largest annual freshwater source there and provide a framework to assess individual freshwater sources in any tide-water system.

    Nat. Geosci. 10.1038/s41561-017-0018-z (2017).

  6. Marine Conservation

    Reversing a regime shift (or not)

    1. Andrew M. Sugden

    Herbivores are needed to keep the macroalga Sargassum from replacing corals.

    CREDIT: WATERFRAME/ALAMY STOCK PHOTO

    Coral reefs worldwide face many challenges. One of these, brought on by declines in herbivore populations on reefs, is a tendency to shift from dominance by live corals to dominance by macroalgae. Loffler and Hoey, in a study of the leathery brown macroalga Sargassum on Australia's Great Barrier Reef, show how hard it is to reverse this regime shift. Physical removal of the Sargassum canopy, simulating the activity of storms, had a negligible effect, and even removal of the alga's “rooting” holdfasts was only a temporary setback to the Sargassum community. To improve the likelihood of restoring the coral community, physical removal needs to be accompanied by herbivore activity.

    J. Ecol. 10.1111/1365-2745.12875 (2017).

  7. Physics

    Probing an excitonic insulator

    1. Jelena Stajic

    In semiconductors and semimetals, the negatively charged electrons and positively charged holes carry electrical current by moving in opposite directions. However, if electrons and holes were to form electrically neutral pairs, the material might stop conducting electricity and become an (excitonic) insulator. Du et al. explored this possibility in InAs/GaSb quantum wells, where electrons reside in the InAs layer and holes in the GaSb layer. Transmission spectroscopy in combination with transport measurements revealed the presence of an energy gap, which responded to the application of a magnetic field as one would theoretically expect for an excitonic insulator. The topologically nontrivial band structure of this system indicates that it might be a topological excitonic insulator.

    Nat. Commun. 10.1038/s41467-017-01988-1 (2017).