Editors' Choice

Science  05 Aug 2016:
Vol. 353, Issue 6299, pp. 554
  1. Infectious Diseases

    How antibiotic resistance spreads

    1. Julia Fahrenkamp-Uppenbrink

    Resistance of Shigella bacteria to antibiotics is a growing problem.

    PHOTO: SCIENCE SOURCE

    Shigella bacteria cause diarrheal illnesses in about 125 million people each year, particularly in developing countries. Antibiotics are widely used to prevent complications and reduce spreading of the disease, but resistance to the antibiotic ciprofloxacin is an increasing problem. The et al. report whole-genome sequencing of 60 ciprofloxacin-resistant S. sonnei bacteria from Vietnam, Bhutan, Thailand, Cambodia, Australia, and Ireland. They show that the bacteria all belong to the same lineage, one that probably originated in South Asia. This lineage emerged in a single clonal event and has since spread widely across Asia and beyond.

    PLOS Med. 10.1371/journal.pmed.1002055 (2016).

  2. Neuroimmunology

    Neural inputs shape gut immunity

    1. Kristen L. Mueller

    Immune cells called innate lymphoid cells (ILCs) are important peacekeepers in the gut. For instance, they help prevent microbial contents from leaking through the intestinal epithelial barrier. Ibiza et al. now report that, at least in mice, ILCs carry out this function with the aid of neural inputs. They found that ILCs express an enzyme on their surface called RET that responds to proteins secreted by glial cells in the gut. Mice engineered to lack RET expression in ILCs secreted less interleukin-22, a protein that promotes gut epithelial integrity, and fared worse in an experimental colitis model or when infected with the enteric pathogen Citrobacter rodentium. Thus, a multitissue defense unit helps defend the complex microenvironment of the gut.

    Nature 535, 440 (2016).

  3. Rock Mechanics

    Printing out the pores

    1. Brent Grocholski

    The diversity of three-dimensional (3D) printing applications now includes fabricating porous rocks. The organization of pore space in rocks strongly influences their strength and fluid flow through them. Head and Vanorio constructed virtual 3D images of rocks by using x-ray tomography, which they followed with a series of pore microgeometry modifications and 3D printing of samples. Measurements of fluid flow through the samples brings deeper understanding to how processes such as mineral precipitation and compaction clog up the pore network. This technique helps reverse-engineer how rocks get their pore structure and offers a method for measuring flow properties through delicate samples.

    Geophys. Res. Lett. 10.1002/2016GL069334 (2016).

  4. Cancer Biology

    For metastasis, accessibility matters

    1. Paula A. Kiberstis

    Each year, over 200,000 people die of small cell lung cancer (SCLC). These tumors grow aggressively, and most patients are diagnosed after metastasis has already occurred. Denny et al. explored potential mechanisms driving metastasis of SCLC by studying a mouse model of the human disease. They conclude that primary tumor cells acquire a propensity to metastasize at least in part through large-scale remodeling of their chromatin state. The experiments revealed a large increase in chromatin accessibility in liver metastases compared with primary SCLC cells. This change correlated with increased expression of a transcription factor called NFIB, and binding sites for NFIB were enriched in the open regions of chromatin. Conceivably, these regions could help pinpoint genes required for metastasis.

    Cell 166, 328 (2016).

  5. Polymer Chemistry

    Reactive crystals have the edge

    1. Phil Szuromi

    A recently reported strategy for making two-dimensional polymer crystals uses a rigid monomer with three photoreactive anthracene arms that polymerize through cycloaddition. Like the end groups of a linear polymer, the reactive anthracene edge groups should only be along the rim of the hexaprismatic crystals that form, and not on the faces. Zhao et al. show that this is indeed the case by decorating the edges of these two-dimensional crystals with a dye. A maleic anhydride derivatized with a BODIPY (boron-dipyrromethene) dye reacts with the crystals through a Diels-Alder reaction. The dye, which fluoresces in a wavelength range outside of that of the self-fluorescence of the crystal, is observed only on the edges.

    J. Am. Chem. Soc. 10.1021/jacs.6b05456 (2016).

  6. Metabolism

    Activated T cells' mitochodria adapt

    1. L. Bryan Ray

    When activated, T lymphocytes increase their mitochondria, in both size and number.

    PHOTO: RON-HAREL ET AL., CELL METABOLISM (12 JULY 2016) © 2016 CELL PRESS

    Proliferation of mitochondria provides not only a way for cells to increase the metabolic function of existing organelles but also an opportunity to adjust the mitochondria for specialized functions. Ron-Harel et al. quantified proteomic changes in the mitochondria of activated mouse CD4+ T cells. To support rapid proliferation of the activated cells, new mitochondria showed an increased abundance of enzymes that participate in folate-mediated one-carbon metabolism. Blocking this pathway by depleting the mitochondrial serine hydroxymethyltransferase enzyme inhibited T cell proliferation and survival. Such remodeling of mitochondrial function, along with replication, may be an important step in how cells adapt to physiological or pathological stimuli.

    Cell Metab. 10.1016/j.cmet.2016.06.007 (2016).

  7. Invasive Species

    Tree pests and pathogens in North America

    1. Andrew M. Sugden

    Oak tree in Big Sur, California affected by sudden oak death fungus

    PHOTO: © RICHARD BROADWELL/ALAMY STOCK PHOTO

    Global trade continually introduces alien species of insects and pathogens throughout the world, often with serious ecological and economic consequences. Lovett et al. analyzed information about the past 150 years of invading forest tree pests in the United States, documenting their means of arrival and their impacts on U.S. trees and forest ecosystems. They estimate that invasive insects continue to arrive in the United States at a rate of 2.5 species annually; of these, about 10% are the particularly damaging wood-boring insects. Pests typically arrive on live plants and in wooden packaging material. Policies for combating such invasions should include cleaning shipments before export and inspections, surveillance, quarantine, and eradication efforts upon entry.

    Ecol. Appl. 26, 1437 (2016).