Editors' Choice

Science  29 Jan 2016:
Vol. 351, Issue 6272, pp. 462
  1. Green Infrastructure

    Saving water—but at what cost?

    1. Nicholas S. Wigginton

    Green potable water systems can harbor elevated levels of pathogens


    Strategies to reduce water consumption in buildings may have some unintended consequences. Rainwater cisterns, solar water heaters, and other similar efforts minimize potable water use and reduce energy consumption, but they may also degrade water quality. In a survey of buildings with various green infrastructure, Rhoads et al. found that water age, which affects residual chlorine levels, pipe corrosion, and even taste, was significantly greater than that in a conventional home. Consistent with those findings, there were also orders of magnitude more opportunistic pathogens such as Legionella species in the green plumbing systems. Reducing water age by eliminating unnecessary storage and regularly flushing pipes may help green water efforts become more widely adopted.

    Environ. Sci. Water Res. Technol. 10.1039/C5EW00221D (2016).

  2. Education

    Flipping for higher exam scores

    1. Melissa McCartney

    Active problem-solving in a collaborative environment leads to more effective learning than a traditional lecture. Weaver and Sturtevant report on a 3-year study of a flipped chemistry majors' sequence (lectures are watched outside of class and students participate in group problem-solving and whole-class discussions during scheduled class time). Results collected from standardized exams showed that the grades of students in the flipped class were significantly higher than those of students in the traditional class. Data collected on the student perspective stressed the importance of carefully planning how the course is taught and carried out, as this will influence the effect it has on students. Overall, this study supports the idea that larger-enrollment courses can be taught using a flipped model.

    J. Chem. Educ. 10.1021/acs.jchemed.5b00316 (2015).

  3. Pain

    A double-drug approach for chronic pain

    1. Peter Stern

    Chronic pain is a major reason why people visit a doctor. Unfortunately, the underlying causes of chronic pain are still poorly understood. To gain more insight, Ren et al. studied a mouse model of neuropathic pain. Nerve injury resulted in a rewiring of neuronal circuits in a region of the brain called the nucleus accumbens, which regulates emotions and addictive behavior. The excitability of some neurons increased, but their number of excitatory synapses fell. Nerve injury also led to reduced extracellular dopamine concentrations in the nucleus accumbens. Combined treatment of mice with dopamine receptor antagonists and a nonsteroidal anti-inflammatory drug blunted neuropathic pain, suggesting potential new drug combinations for treating chronic pain.

    Nat. Neurosci. 10.1038/nn.4199 (2015).

  4. Materials Science

    Bandages to aid diabetic wound healing

    1. Marc S. Lavine

    For some conditions, such as diabetic foot ulcers, wound healing can take a long time and may be delayed by the overexpression of proteases such as matrix metalloproteinase-9 (MMP-9). Castleberry et al. used layer-by-layer technology to first deposit a water-degradable underlayer onto a nylon bandage, over which they then coated alternating layers of chitosan and small interfering RNA (siRNA). The release profile of the siRNA was controlled by the thickness of the underlayer, whereas the number of siRNA layers could be used to control the overall dose. In mouse models, local delivery of siRNA to an ulcerative wound reduced the production of MMP-9 and thus increased the concentration of extracellular matrix and dramatically improved wound healing.

    Adv. Mater. 10.1002/adma.201503565 (2015).

  5. Epigenomics

    Our varied methylome

    1. Laura M. Zahn

    Differential methylation of genes has been associated with disease and may play a role in the phenotypic variation between individuals. In order to survey global methylation and to understand how genetic versus nongenetic factors affect methylation, Busche et al. used whole-genome bisulfide sequencing on adipose and blood samples from identical and fraternal twins. Although methylation patterns in tissues showed a high degree of similarity between individuals, the authors did find that 15 to 20% of the tissue methylome varied across individuals, primarily in gene enhancers. More surprisingly, in cases where the environment determined methylation, approximately 60% of the observed variation was unique to the individual.

    Genome Biol. 16, 290 (2015).

  6. Cell Migration

    Dendritic cells have two ways to tango

    1. Stella M. Hurtley

    The activation status of dendritic cells determines how they migrate


    Immature dendritic cells reside in peripheral tissues and use their high migratory capacities to sniff out danger-associated antigens; when they encounter antigens, dendritic cells mature and rapidly migrate to lymph nodes to initiate the adaptive immune response. Vargas et al. show that a switch in actin nucleating machineries adapts the dendritic cell migration mode. Arp2/3 nucleates actin at the front of immature dendritic cells, and dendritic cells require it for antigen uptake, but Arp2/3 reduces cell speed and persistence. Mature dendritic cell rely on the formin mDia1 to migrate. mDia1 changes locomotion from diffusive migration to a persistent random walk. This transition helps mature dendritic cells to move along chemokine gradients toward the lymph nodes.

    Nat. Cell Biol. 18, 43 (2016).

  7. Synthetic Biology

    Engineering a bacterial “Deadman” walking

    1. Valda Vinson

    One of the most successful areas of synthetic biology is modifying microorganisms for applications in biotechnology. However, these engineered microbes could pose a risk if released into open environments. To overcome this, Chan et al. engineered two modular gene circuits into the bacteria Escherichia coli that act as kill switches. The “Deadman” circuit requires a specific small molecule to prevent a toxin from being expressed and killing the cell. In the “Passcode” circuit, small molecules must induce two transcription factors to inhibit toxin expression. An advantage over other biocontainment systems is that these circuits can be reprogrammed to respond to different inputs or to induce different killing mechanisms.

    Nat. Chem. Biol. 10.1038/NCHEMBIO.1979 (2015).

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