Editors' Choice

Science  04 Dec 2015:
Vol. 350, Issue 6265, pp. 1218
  1. Oil Spills

    Dispersants suppressed oil degradation

    1. Nicholas S. Wigginton

    Airplane applying oil dispersant off the Louisiana coast

    PHOTO: PATRICK SEMANSKY/APIMAGES

    The 2010 Deepwater Horizon blowout released hundreds of millions of liters of oil into the Gulf of Mexico. One of the main mitigation strategies to prevent oil from reaching the shore—and potentially to stimulate natural bacterial communities capable of degrading oil and gas—was the application of 7 million liters of chemical dispersant. At the time, little was known about the effect these dispersants might have on hydrocarbon biodegradation rates. In a series of laboratory experiments, Kleindienst et al. observed that the same dispersant used in 2010 actually suppresses the major hydrocarbon-degrading groups in favor of dispersant-degrading bacteria. This confounding effect of dispersants therefore may explain why field data collected during the spill showed lower than expected biodegradation of oil and gas.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1507380112 (2015).

  2. Metabolic Disease

    Inflammation improves insulin resistance

    1. Kristen L. Mueller

    One of the hallmarks of diabetes is insulin resistance, a condition in which insulin accumulates because the body cannot effectively use it. Although insulin resistance occurs in both age- and obesity-associated diabetes, Bapat et al. now report that the underlying cellular mechanisms that drive these diseases differ. An overzealous inflammatory response contributes to obesity-associated insulin resistance. In contrast, an immunosuppressive subset of T cells, called regulatory T cells (Tregs), promoted insulin resistance in aging mice. Aged but not obese mice that lacked these cells experienced improvement in multiple metabolic parameters. Scientists will need to determine whether Tregs in adipose tissue contribute to age-associated insulin resistance in humans and how they may do so.

    Nature 10.1038/nature16151 (2015).

    Suppressor T cells in fat tissue promote metabolic disease in aging mice

    PHOTO: STEEX/ISTOCK PHOTO
  3. Protein Engineering

    Engineering enzymes to stand alone

    1. Valda Vinson

    Enzymes efficiently synthesize many useful compounds. However, in many cases, their need to associate with other proteins limits their biosynthetic utility outside of cells. Buller et al. used directed evolution (a method of protein engineering that mimics of the process of natural selection) to increase the catalytic activity of the β subunit of the tryptophan synthase complex (TrpB). TrpB makes l-tryptophan from l-serine and indole but is inefficient on its own. Mutations that restored activity to TrpB alone act through the same mechanism as partner protein binding. Both use a mechanism called allostery, in which changes distant from the active site affect enzymatic activity. The standalone TrpB provides a simplified platform to produce noncanonical amino acids.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1516401112 (2015).

  4. Transcription

    Plants chemically modify their mRNAs

    1. Laura M. Zahn

    When Arabidopsis plants respond to stress, they often chemically modify their RNA transcripts; for instance, adding methyl groups to specific ribonucleotides. Such changes can alter RNA function and stability. In order to characterize such modifications on RNAs transcribed from genes, Vandivier et al. performed a high-throughput annotation of modified ribonucleotides within mRNA. They found that modifications were not random but rather distributed to specific types of RNAs, such as on degrading transcripts and long noncoding RNAs, or specific sites within transcripts, such as regions that regulate RNA splicing. Overall, their studies suggest that marks regulate the stability of mRNA transcripts.

    Plant Cell 10. 1105/tpc. 15. 00591 (2015).

  5. X-Ray Optics

    Guiding x-rays on a chip

    1. Ian S. Osborne

    For visible, infrared, and ultraviolet wavelengths of light, the ability to guide the light is very well served by a variety of mature platforms such as waveguides, optic fibers, and photonic crystals. Going to shorter wavelengths such as x-rays, however, provides a formidable challenge, because the light is penetrating and readily escapes attempts at confinement. By fabricating engineered channels in a layer of tantalum using electron beam lithography, Salditt et al. demonstrate the ability to guide hard x-rays in the curved waveguides and show that they can do so with channels of surprisingly small radii of curvature. The demonstration shows the possibility of extending the functionality of integrated optics to the x-ray regime.

    Phys. Rev. Lett. 115, 203902 (2015).

  6. Cancer

    Tumors evolve free of Darwinian constraints

    1. Guy Riddihough

    Mutations help shape how tumors evolve. What constrains the diversity of these mutations is less clear. Ling et al. determined the spectrum of single-nucleotide variations in 286 samples from a single heptaocellular carcinoma tumor. They then modeled how mutations accumulated in tumors using population genetic theory. Their analysis predicted that the tumor harbored more than 100 million mutations. Such high genetic diversity suggests that the tumors evolve in a non-Darwinian manner, because Darwinian evolution generally reduces genetic diversity within a population. These results imply that microscopic tumors are likely to be highly diverse, suggesting that even these tumors could quickly develop resistance in the face of therapy.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1519556112 (2015).

    Reversible surface configurations in a two-component network

    PHOTO: LEE ET AL., ACS NANO (9 NOVEMEBER 2015) © 2015 AMERICAN CHEMICAL SOCIETY
  7. Materials Science

    Switching locally or globally

    1. Marc S. Lavine

    Dynamic materials that can switch between two or more states have found a range of applications, from shape-memory materials to those with changeable surface adhesion properties. Lee et al. explore the properties of 1,3,5-tris(4-carboxyphenyl)benzene (BTB) absorbed from solution onto the surface of freshly cleaved, highly oriented pyrolytic graphite. BTB forms an open network structure and is able to accommodate polyaromatic guest molecules. However, though the application of a voltage bias, the network structure collapses, squeezing out the guest molecules in the local region. The same squeezing effect can also be achieved globally, by changing the temperature, thus giving two ways to tune the overall surface properties.

    ACS Nano 10.1021/acsnano.5b06081 (2015).