This Week in Science

Science  10 Nov 2017:
Vol. 358, Issue 6364, pp. 758
  1. Cholera

    Wave upon wave of disease

    1. Caroline Ash

    The spread of cholera is consistent with person-to-person transmission rather than environmental contamination.

    CREDIT: STEVE RAYMER/NATIONAL GEOGRAPHIC CREATIVE

    The cholera pathogen, Vibrio cholerae, is considered to be ubiquitous in water systems, making the design of eradication measures apparently fruitless. Nevertheless, local and global Vibrio populations remain distinct. Now, Weill et al. and Domman et al. show that a surprising diversity between continents has been established. Latin America and Africa bear different variants of cholera toxin with different transmission dynamics and ecological niches. The data are not consistent with the establishment of long-term reservoirs of pandemic cholera or with a relationship to climate events.

    Science, this issue p. 785, p. 789

  2. Ice Sheets

    Disappearance of an ice sheet

    1. H. Jesse Smith

    The Cordilleran Ice Sheet is thought to have covered westernmost Canada until about 13,000 years ago, even though the warming and sea level rise of the last deglaciation had begun more than a thousand years earlier. This out-of-phase behavior has puzzled glaciologists because it is not clear what mechanisms could account for it. Menounos et al. report measurements of the ages of cirque and valley glaciers that show that much of western Canada was ice-free as early as 14,000 years ago—a finding that better agrees with the record of global ice volume (see the Perspective by Marcott and Shakun). Previous reconstructions seem not to have adequately reflected the complexity of ice sheet decay.

    Science, this issue p. 781; see also p. 721

  3. DNA Replication

    Metabolic regulation of genome stability

    1. Steve Mao

    Cells respond to metabolic fluctuations by adjusting the speed of DNA replication as a safeguard for genome stability. Somyajit et al. elucidate the cellular mechanisms that align replication fork dynamics with metabolic pathways (see the Perspective by Gómez-González and Aguilera). The elevation of reactive oxygen species (ROS) levels under metabolic stress dissociates a replication accelerator from the replisome and leads to replication slowdown, thus preventing replication stress. Studying this genome surveillance mechanism in cancer cells with elevated ROS levels and increased replication adaptability may provide opportunities to specifically target tumors.

    Science, this issue p. 797; see also p. 722

  4. Political Science

    Measuring the impact of the media

    1. Gilbert Chin

    The active participation of the people is one of the central components of a functioning democracy. King et al. performed a real-world randomized experiment in the United States to understand the causal effect of news stories on increasing public discussion of a specific topic (see the Policy Forum by Gentzkow). Social media posts increased by almost 20% the first day after the publication of news stories on a wide range of topics. Furthermore, the posts were relatively evenly distributed across political affiliation, gender, and region of the United States.

    Science, this issue p. 776; see also p. 726

  5. Scientific Community

    Evaluating author contribution statements

    1. Aaron Clauset

    Many journals require an author contribution statement that identifies who did what in the project. However, journals have different policies and practices, so it is unclear whether these statements add consistent value beyond the order of the authors. To quantify their utility and perceived value, Sauermann and Haeussler used data from more than 12,000 author contribution statements and surveyed 6000 corresponding authors. Author order correlated strongly with the breadth and type of author contribution, and most researchers, especially those at junior levels, saw value in the statements. However, author order was still perceived as a better indicator of contribution importance and was still favored when evaluating others.

    Sci. Adv. 10.1126/sciadv.1700404 (2017).

  6. Optics

    Scattered light, it is all the same

    1. Ian S. Osborne

    Materials can vary from transparent to opaque depending on the density of scatters within the medium. As light propagates through a material, intuition might suggest that the more scatters there are, the shorter the path along which the light can propagate. Savo et al. confirm a recent theoretical proposal that predicts that this is not the case. They shone light through a series of samples of varying scatterer density and found that the average path length that the light traveled was independent of the sample microstructure. This finding should also be applicable to acoustics and matter waves.

    The distance that light waves travel is independent of scatterer density.

    CREDIT: SAVO ET AL.

    Science, this issue p. 765

  7. Cancer

    De-stressing cancer with β-blockers

    1. Yevgeniya Nusinovich

    Common wisdom holds that stress is not good for cancer patients. However, stress can be difficult to avoid, considering that both the diagnosis of cancer and the associated treatments are quite challenging for the mind and body. Nilsson et al. investigated the potential effects of stress hormones during treatment of non–small cell lung cancer. Stress hormones activate β2-adrenergic receptors on cancer cells, triggering a signaling cascade that promotes tumor resistance to EGFR (epidermal growth factor receptor) inhibitors, a key therapy for this disease. Conversely, β-blockers, a common class of drugs used in humans, blocked this mechanism of resistance and may become a useful adjunct to lung cancer therapy regimens.

    Sci. Transl. Med. 9, eaao4307 (2017).

  8. Computer Science

    Fly brain inspires computing algorithm

    1. L. Bryan Ray

    Flies use an algorithmic neuronal strategy to sense and categorize odors. Dasgupta et al. applied insights from the fly system to come up with a solution to a computer science problem. On the basis of the algorithm that flies use to tag an odor and categorize similar ones, the authors generated a new solution to the nearest-neighbor search problem that underlies tasks such as searching for similar images on the web.

    Science, this issue p. 793

  9. Topological Matter

    Topological or trivial?

    1. Jelena Stajic

    Evidence for Majorana bound states (MBS), which are expected to provide a platform for topological quantum computing, has been found in several material systems. Typically, the experimental signature is a peak in the spectrum at zero energy, but mechanisms other than MBS need to be carefully ruled out. Using spin-polarized scanning tunneling spectroscopy, Jeon et al. studied chains of iron atoms deposited on superconducting lead and found a more distinctive signature of the topological states. Unlike trivial zero-energy states, MBS exhibited a characteristic spin-polarization signal.

    Science, this issue p. 772

  10. Solar Cells

    Transporter layers improve stability

    1. Phil Szuromi

    Although perovskite solar cells can have power conversion efficiencies exceeding 20%, they can have limited thermal and ultraviolet irradiation stability. This is in part because of the materials used to extract the charge carriers (electrons and holes) from the active layer. Arora et al. replaced organic hole transporter layers with CuCSN to improve thermal stability. Device lifetime was enhanced when a conducting reduced graphene oxide spacer was added between the CuSCN layer and the gold electrode.

    Science, this issue p. 768

  11. Organic Chemistry

    Lewis acid catalysis tackled by tag team

    1. Jake Yeston

    Molecular catalysts with two closely spaced nitrogen-hydrogen groups can act like a tweezer, activating a carbon center by latching onto a leaving group through double hydrogen bonding and then pulling it away. In the resultant ion pair, the shape of the catalyst can bias an ensuing reaction to favor just one of two possible mirror-image products. Banik et al. used this motif to activate a Lewis acid cocatalyst, pulling a leaving group off silicon instead of carbon (see the Perspective by Mattson). The combined pair of catalysts is more effective for reactions such as asymmetric cycloadditions that involve weaker leaving groups on carbon.

    Science, this issue p. 761; see also p. 720

  12. Metabolism

    Regulated lysosomal efflux of amino acids

    1. L. Bryan Ray

    A new technique allows rapid purification of lysosomes and metabolic profiling by liquid chromatography and mass spectrometry. Abu-Remaileh et al. engineered cultured human cells to produce a protein tag on lysosomal membranes that could be used to rapidly precipitate purified lysosomes on magnetic beads. Analysis of their contents under various conditions showed that efflux from the lysosome of most essential amino acids (but not that of most other amino acids) is a regulated process. Amino acid transport was inhibited under conditions of nutrient depletion as a result of inhibition of the mTOR (mechanistic target of rapamycin) protein kinase complex.

    Science, this issue p. 807

  13. Nutrient Sensing

    SAMTOR joins the family

    1. Stella M. Hurtley

    The amino acid methionine is widely appreciated to have interesting effects on animal physiology. Diets low in methionine increase longevity and overall health, particularly glucose homeostasis. Gu et al. describe a potential molecular link between the effects of methionine restriction and the growth controller mTOR complex 1 (mTORC1), a well-validated regulator of life span and health span in many organisms. They identify a protein that they named SAMTOR as a component of the nutrient-sensing pathway upstream of mTORC1. SAMTOR directly binds S-adenosylmethionine (SAM), a metabolite made from methionine, and is necessary for regulating mTORC1 in response to methionine.

    Science, this issue p. 813

  14. Cell Biology

    Taming mitosis for differentiation

    1. Stella M. Hurtley

    The mitotic oscillator consists of molecular switches known to drive cell division forward. This conserved clocklike regulatory circuit has not previously been implicated in cellular processes other than division. Multiciliated cells generate motile cilia-powered flows that are essential for brain, respiratory, and reproductive functions. Al Jord et al. found that the mitotic oscillator was activated in a calibrated fashion in terminally differentiating progenitors of multiciliated cells (see the Perspective by Levine and Holland). The oscillator function was used to drive massive production of cilia-nucleating centrioles while avoiding mitotic commitment. Thus, mammalian postmitotic progenitors can recruit and calibrate the mitotic oscillator to impose timing and directionality of cellular differentiation instead of proliferation.

    Science, this issue p. 803; see also p. 716

  15. Invasive Species

    Humans shape how plants invade

    1. Julia Fahrenkamp-Uppenbrink

    Human activities are introducing alien species to ecosystems around the world at an increasing rate. Some of these species become invasive and cause economic or environmental harm. In a Perspective, Kueffer explains that human influence extends beyond the introduction of alien species to affect how such species spread across landscapes and which become invasive. Reframing invasion theories to take full account of these influences will help to explain and predict which species are likely to become invasive and where.

    Science, this issue p. 724

  16. Neuroendocrinology

    Connecting smell to metabolism

    1. Gemma Alderton

    There is accumulating evidence, particularly in rodents, that odor perception and olfactory neurons can regulate metabolism. For instance, ablating the sense of smell can lead to resistance to obesity induced by a high-fat diet. In a Perspective, Garrison and Knight discuss the potential mechanisms and implications of these findings with regard to the regulation of metabolism and how this may also affect longevity in mammals.

    Science, this issue p. 718

  17. Fragile X Syndrome

    Balancing translation and Rac1 signaling

    1. Leslie K. Ferrarelli

    The neurological dysfunction and intellectual disability of fragile X syndrome (FXS) is caused by loss of the mRNA translation repressor FMRP. Santini et al. found that loss of FMRP enhanced protein synthesis mediated by the translation-initiating factor eIF4E. As a result, the actin polymerization dynamics necessary for synaptic plasticity and learning were impaired. The peptide 4EGI-1, which inhibits the formation of eIF4E-mediated translational machinery, improved hippocampal synaptic function, dendritic morphology, and learning behaviors in FXS model mice.

    Sci. Signal. 10, eaan0665 (2017).

  18. Fungal Infection

    Calibrating antifungal responses

    1. Anand Balasubramani

    Immune responses to fungal infections are complicated by the fact that fungi can exist in multiple forms depending on environmental cues. Verma et al. evaluated innate immune responses to Candida albicans, a fungus that transitions from a single-celled yeast form to filamentous hyphae as infection progresses. Candidalysin, a hyphae-associated protein and virulence factor, served as a danger signal that potentiated the immune response to C. albicans. Candidalysin-deficient strains caused minimal epithelial damage and elicited a strongly blunted type-17 immune response. Thus, the innate antifungal responses to C. albicans are driven by a synergy between cellular damage triggered by candidalysin that is further amplified by interleukin-17–driven inflammation.

    Sci. Immunol. 2, eaam8834 (2017).