Editors' Choice

Science  31 Mar 2017:
Vol. 355, Issue 6332, pp. 1387
  1. Applied Ecology

    Common antibiotic hurts bee survival

    1. Barbara R. Jasny

    Several factors have been identified that could be responsible for the collapse of honeybee populations. However, Raymann et al. have identified an antibiotic that appears to reduce bee survival by changing the bee microbiome. Hives are frequently treated with tetracycline to prevent infections. When bees were fed tetracycline for 5 days in a laboratory and reintroduced to their hives, half as many survived after 3 days, relative to controls. Antibiotic treatment decreased the number and relative abundance of the bacteria living in the bee gut. After treatment, bees were more sensitive to infection by a Serratia species of bacterial pathogen. Bees that were germ-free showed no changes after tetracycline treatment, suggesting that tetracycline was acting on the microbiome and not directly on the bees.

    PLOS Biol. 10.1371/journal.pbio.2001861 (2017).

  2. Cancer

    Metastatic cells feed off a complement

    1. Paula A. Kiberstis

    Cancer patients with metastases in the cerebrospinal fluid (CSF) have a poor prognosis. How cancer cells survive in the CSF has been an enigma because this microenvironment is devoid of mitogens and nutrients required for cell growth. Studying mice and patient samples, Boire et al. show that cancer cells metastasizing to the CSF overexpress a protein called complement component 3 (C3). C3 activates a specific receptor in the choroid plexus epithelium, a barrier system in the brain that prevents cells and molecules in the blood from entering the CSF. This activation disrupts the blood-CSF barrier, allowing circulating growth factors into the CSF. A drug that blocks this activation suppressed metastasis to the CSF in mice.

    Cell 168, 1101 (2017).

  3. Biomaterials

    Separating chemistry from mechanics

    1. Marc S. Lavine

    Hydrogels based on hyaluronic acid (HA), a major component of cartilage extracellular matrix, are a logical choice for making injectable matrices for cartilage regeneration. However, when one changes the concentration of HA, and thus the chemical cues presented to the cell, this also changes the mechanics of the gels, and both factors influence cell proliferation. Zhu et al. used a modified elastin-like protein to form a gel with HA so that the concentration of HA could be adjusted without affecting the gel stiffness. With increasing HA, they found a dose-dependent increase in cartilage marker gene expression and enhanced sGAG deposition, with minimized undesirable fibrocartilage characteristics.

    Biomaterials 10.1016/j.biomaterials.2017.02.010 (2017).

  4. Genetics

    Manipulating the fly conditionally

    1. Beverly A. Purnell

    The fruit fly Drosophila has been indispensable in the genetics and biochemical toolkits. This model organism has enabled many advances in understanding early development, metabolism, cell biology, evolution, and so much more. However, most knockout methods fail to completely eliminate gene function and do not work in differentiated cells. Fisher et al. developed “FlpStop” for conditional gene disruption and gene rescue. They showed proof of principle by generating conditional null alleles for the wing development gene apterous. Follow-up analyses manipulated genes involved in GABAergic neurotransmission or neuronal excitability within different cell types or cellular compartments. The tool can now be applied to other differentiated or undifferentiated cells at specific times of development to better understand the interactions between genes and within genetic networks.

    eLife 10.7554/eLife.22279.001 (2017).

  5. Microbiota

    Gut churning controls inflammation

    1. Caroline Ash

    The gut is not an inert tube. It undergoes regular contractions called peristalsis. Rolig et al. examined the constant movement in the zebrafish gut and asked whether the enteric nervous system (ENS) plays a role in regulating the microbiota, as well as food flow. If the zebrafish ENS was disabled by knocking out the gene sox10, intestinal neutrophils accumulated, the gut epithelium proliferated, and inflammation resulted. The inflammation was caused by overgrowth of some bacterial lineages and was resolved by transplantation of ENS precursors or when a well-adapted anti-inflammatory bacterial strain was given to the fish. Thus, peristalsis is important for supressing the growth of poorly symbiotic bacteria, in zebrafish at least.

    PLOS Biol. 10.1371/journal.pbio.2000689 (2017).

  6. Water Chemistry

    Neon nudges clusters toward bulk liquid

    1. Jake Yeston

    It is hard to get a global sense of what is happening at the molecular level in a drop of water. The hydrogen bonds responsible for the molecules' mutual attraction are in a constant state of flux. Chemists have learned a lot about the underlying structure by studying cold, isolated clusters that contain just a few molecules at a time. However, these clusters sometimes close in on themselves in tighter arrangements than the bulk liquid typically hosts. Douberly et al. show that a neon atom can nudge water tetramers formed in helium droplets to adopt the more open geometries prevalent in the bulk, facilitating detailed study of these motifs.

    J. Am. Chem. Soc. 10.1021/jacs.7b00510 (2017).

  7. Education

    3D assessment: The future is here

    1. Melissa McCartney

    Science education reforms for kindergarten through 12th grade focus on three-dimensional learning (3D-L), comprising scientific and engineering practices, crosscutting concepts, and disciplinary core ideas. These reforms also exist in undergraduate science, technology, engineering, and math (STEM) programs, and faculty interested in bringing 3D-L to their classrooms need a way to assess student learning. Laverty et al. have developed the Three-Dimensional Learning Assessment Protocol (3D-LAP) for use in introductory biology, chemistry, and physics courses at the undergraduate level. The 3D-LAP allows users to characterize the potential of assessment tasks to determine whether students engage with 3D-L and can also be used as a professional development tool for faculty interested in designing new assessments. The 3D-LAP is also ideal for characterizing how assessments change over time with respect to STEM transformation efforts.

    PLOS ONE 10.1371/journal.pone.0162333 (2016).

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