This Week in Science

Science  16 Sep 2016:
Vol. 353, Issue 6305, pp. 1245
  1. Sensory Biology

    Swapping senses to avoid the din

    1. Sacha Vignieri

    Fringe-lipped bats can swap senses to hunt frogs.

    PHOTO: MERLIN D. TUTTLE/SCIENCE SOURCE

    Species that use sound for foraging or movement are at a disadvantage in our increasingly noisy world. However, some species have the capacity to operate despite background din. Fringe-lipped bats typically hunt frogs by listening for their breeding calls. In noisy environments, Gomes et al. found that the bats shift from passive acoustic reception of the frogs' sounds to using echolocation to detect the calling frogs' expanding throat sacs.

    Science, this issue p. 1277

  2. Brain Microcircuits

    Neuronal assembly dynamics in the brain

    1. Peter Stern

    Sharp-wave ripples are a form of neuronal activity pattern observed in the hippocampus that may play a role in memory consolidation. To investigate this phenomenon, Malvache et al. simultaneously imaged calcium dynamics in multiple hippocampal neurons of live mice. A category of neurons called place cells became active when mice ran on a treadmill. When the mice paused, fast replay events occurred that recalled the sequence of cell activations while the mice were running, and these coincided with the sharp-wave ripples. Reactivation periods in which different assemblies of cells took part were also observed. Imaging of the mice indicated that patches of neurons might cooperate to produce fragments of the ripple events.

    Science, this issue p. 1280

  3. Extinction

    Like in scale, different in pattern

    1. Sacha Vignieri

    Before now, there have been five major extinction events in Earth's history. Understanding the patterns and processes that characterized the previous extinctions are important for understanding, and perhaps mitigating, the levels of extinction occurring now. Payne et al. looked at marine taxa, including vertebrates and mollusks, and found several important differences. Most notably, current extinctions are centered on large-bodied species, irrespective of their life-history strategy. This makes sense considering that the main drivers of marine extinctions today are human hunters and fishers, rather than climate—at least so far.

    Using fossils can help to understand present-day extinction patterns.

    PHOTO: M. BOND/SCIENCE SOURCE

    Science, this issue p. 1284

  4. Quantum Simulation

    Staring antiferromagnetism in the face

    1. Jelena Stajic

    Quantum gas microscopy affords a direct, site-resolved view of atoms in an optical lattice. The possibilities for studying quantum phases appear endless, with a major goal being the achievement of d-wave superfluidity akin to the high-temperature superconductivity of cuprate compounds. Three groups have made important progress toward this goal by directly imaging antiferromagnetic correlations, which also appear in the cuprate phase diagram. Parsons et al. did so in a two-dimensional (2D) lattice of fermionic atoms near half-filling, whereas Boll et al. investigated 1D chains. Additionally, Cheuk et al. revealed the influence of doping on the charge correlations in a 2D lattice. Reducing the temperature further should bring these experiments closer to the superfluid regime.

    Science, this issue pp. 1253, 1257, and 1260

  5. Polymer Science

    Stretching the connections

    1. Marc S. Lavine

    Measuring the elastic behavior of polymers is complicated by their long chain architecture, which can lead to transient entanglements and time-dependent behavior. A further complication arises in the case of covalently linked polymers, such as hydrogels, that contain fixed loop defects. By controlling defect structure during polymer synthesis, Zhong et al. can count the defects in a polymer gel and correlate them to elastic and rheological behavior. Current models are not able to capture their observations, but a real elastic network theory, based on a modified phantom network theory, can account for the impact of topological molecular defects.

    Science, this issue p. 1264

  6. Marine Microbiome

    Functional microbial distribution in the ocean

    1. Caroline Ash

    Bucketsful of genome data for marine microorganisms are available. Although taxonomic patterns in the data are carefully sifted for meaning, Louca et al. show that taxonomy alone does not represent community structure. Meta-analysis of the data gathered during the Tara Oceans project classified over 30,000 bacteria and archaea into functional metabolic groups ranging from photoautotrophy and nitrogen fixation to sulfate respiration. Disentangling functional variation from taxonomic variation indicates that environmental conditions select from a global marine “seedbank” for function, not taxonomy.

    Functional and taxonomic variation can be distinguished in Tara Oceans microbiome data.

    PHOTO: CHRISTIAN SARDET

    Science, this issue p. 1272

  7. Nanomaterials

    Brushing out uniform nanorods

    1. Marc S. Lavine

    An ongoing challenge for the synthesis of nanomaterials is to find ways to control their chemistry, architecture, and dimensions while still producing uniform products in reasonable quantities. Pang et al. devise a clever strategy that uses bottlebrush block copolymers to guide material growth from the inside out (see the Perspective by Houlton). Because the polymers can be grown with a narrow size distribution, they act as uniform templates for a variety of precursors. A wide range of materials can be grown, including those that have metallic, ferroelectric, photonic, semiconducting, luminescent, thermoelectric, magnetic, or a combination of properties.

    Science, this issue p. 1268; see also p. 1204

  8. Immunology

    Uncovering how a drug works

    1. John F. Foley

    The drug dimethyl fumarate (DMF) is used to treat autoimmune diseases, including psoriasis and multiple sclerosis, and may act by modifying cysteine residues in proteins. A better understanding of how it works is required because its use has led to life-threatening infections in some patients. Blewett et al. identified cysteine residues in human T cell proteins that reacted with DMF. They found that modification of the kinase PKCθ by DMF prevented PKCθ from mediating full T cell activation.

    Sci. Signal. 9, rs10 (2016).

  9. Genome Editing

    A useful AID for genome editing

    1. Guy Riddihough

    The prokaryotic CRISPR-Cas adaptive immune mechanism has revolutionized genome editing, but some glitches remain. The Cas nuclease is directed to its target site by a guide RNA, which then nicks the DNA. Repair of this cut can generate small unwanted insertions and deletions. Nishida et al. circumvent the problem of inaccurate repair by using a mutated form of the Cas nuclease from a different species, fused to an ortholog of activation-induced cytidine deaminase (AID), which is part of the vertebrate immune system (see the Perspective by Conticello and Rada). The AID ortholog catalyzes nucleotide substitutions at the targeted locus without cutting the DNA, thus reducing off-target effects and improving the efficiency of the CRISPR-Cas toolbox.

    Science, this issue p. 1248; see also p. 1206

  10. Food System

    Good to eat, good for the planet

    1. Julia Fahrenkamp-Uppenbrink

    Food production, processing, and use are responsible for about a quarter of global greenhouse gas emissions. In a Perspective, Garnett considers how the food system can be changed to become more sustainable while also providing for healthy diets. Existing studies highlight the high environmental impacts and damaging health effects of typical Western diets, which are increasingly consumed around the world. But solutions are less clear-cut because existing research only provides a partial picture of what constitutes a sustainable diet. Furthermore, to be successful, policies must take account of the values that not only shape diets but also underlie research and advocacy.

    Science, this issue p. 1202

  11. Antibiotics

    Treatment by the earful

    1. Yevgeniya Nusinovich

    Otitis media, commonly called ear infection, is a ubiquitous childhood malady that accounts for many pediatrician visits and antibiotic prescriptions. However, it is not always easy to get oral antibiotics into small children. Moreover, systemic antibiotics can cause the development of resistance and other side effects. To address these problems, Yang et al. developed a hydrogel-based system that permits delivery of antibiotics directly into the ear and demonstrated its effectiveness in a chinchilla model of nontypeable Haemophilus influenzae ear infection, a common cause of otitis media. No drug was detected in the animals' blood, confirming the specificity of this local delivery method.

    Sci. Transl. Med. 8, 356ra120 (2016).

  12. Infection

    Pathogen stimulates gut oxygen

    1. Caroline Ash

    Several bacterial pathogens have mobile elements with genes for a syringe-like mechanism called T3SS. The assembled T3SS injects virulence effectors into host cells. Lopez et al. found that a T3SS-injected virulence factor produced by a mouse pathogen provokes inflammation, repair responses, and crypt hyperplasia in the host's gut epithelium. Mature colon cells use oxygen for their physiological role in water absorption, but the immature hyperplastic colonocytes do not need oxygen for growth. Hence, during hyperplasia, there is increased availability of oxygen for aerobic pathogens to grow, and the resident anaerobic microbiota is excluded. The pathogens also benefit from using carbon sources that are unavailable to organisms that rely on fermentation for growth.

    Science, this issue p. 1249