Editors' Choice

Science  17 Feb 2012:
Vol. 335, Issue 6070, pp. 776
  1. Microbiology

    Live to Divide Another Way

    1. Caroline Ash

    Bacterial cell division is classically thought of as symmetrical. Several species divide by polar budding, however, and mutations in the cell division machinery of Agrobacterium, Brucella, and Sinorhizobium trigger branching morphologies rather than filaments. Two recent papers explored this phenomenon. First, in the rod-shaped plant pathogen Agrobacterium tunefaciens, Brown et al. used time-lapse photography and observed that new daughter cells emerge strictly from the pole of the mother cell, growing by incorporation of newly synthesized cell wall. After division, there is only a small increase in mother cell length, which retains old cell wall material. Cell division in Mycobacterium was also shown to be asymmetrical, giving rise to slow-growing daughter cells that are less sensitive to an anti-tuberculosis drug than faster-growing but older mother cells (see Aldridge et al., Reports, Science, 6 January 2012). Asymmetric inheritance of cell material of different ages may give bacteria multiple adaptive options by generating a variety of phenotypes, some of which will be able to escape a shift in environmental conditions and live to divide another day.

    Proc. Natl. Acad. Sci. U.S.A. 109, 1697 (2011).

  2. Cell Biology

    A Collective Movement

    1. L. Bryan Ray

    Migratory cells are exquisitely sensitive to gradients in concentrations of molecules that provide guidance cues, and in individual cells, localized signals produce directed migration. Cells sometimes migrate as a group, however, and in this case the signaling mechanisms by which cellular movements are controlled are less clear. Inaki et al. tested whether one member of a group of cells could coordinate migration of the group. The authors modified border cells of the Drosophila ovary so that they would be unresponsive to the endogenous ligands that guide them through the activation of receptor tyrosine kinases. They then overexpressed a receptor in only one of the cells, which resulted in its being active in the absence of ligand. In an alternative approach, the authors activated the small guanosine triphosphatase Rac, which is required for migration, in only one cell. In both cases, signaling in a single cell could direct migration. These results suggest that information directing the group of cells is encoded in the difference between signals occurring in individual cells within the group; these signals appear to be different than the signals used by cells migrating on their own.

    Proc. Natl. Acad. Sci. U.S.A. 109, 2027 (2012).

  3. Psychology

    What Would Jesus Do?

    1. Gilbert Chin

    During the past several election cycles in the United States, the association of religious views and voting preferences has been noted. This has led to claims that greater religiosity generates support for conservative policies, which generally favor lower and less progressive tax rates as well as restrictions on same-sex marriage. The take-home message has been that an individual's religious beliefs influence that person's political stance. Ross et al. have used a survey of roughly 500 liberal and conservative Christians to examine the converse proposition—that an individual's political views affect that person's religious beliefs. What they found was that self-described liberals and conservatives exhibited the expected views regarding higher tax rates and gay marriage. What was intriguing, however, were the views that both liberals and conservatives imputed to a contemporary Jesus: Conservatives rated Jesus as being more in favor of higher taxes on the wealthy and more opposed to gay marriage than they themselves were, with an opposite pattern for liberals. By placing more weight on issues on which they projected Jesus as being more extreme than themselves, individuals on both sides of the spectrum were able to reduce dissonance, which might be better characterized as social rather than cognitive, owing to the collective nature of religion.

    Proc. Natl. Acad. Sci. U.S.A. 109, 10.1073/pnas.1117557109 (2012).

  4. Physics

    Approaching a Supermodel

    1. Jelena Stajic

    Optical lattices, constructed from counter-propagating laser beams and loaded with atoms a fraction of a degree above absolute zero, are slowly fulfilling their potential of simulating solid materials. One of the long-term goals in the field is building a model of a cuprate superconductor, with its layered structure of loosely bound planes. Sommer et al. make a step in that direction by loading a three-dimensional (3D) gas of fermionic atoms of 6Li into a 1D optical lattice; increasing the strength of the optical potential achieves a gradual crossover to a stack of uncoupled 2D layers confined to the successive troughs of the optical lattice. The authors track the formation of the bound pairs of fermions, crucial for the phenomena of superfluidity and superconductivity, by performing rf spectroscopy. As the dimensionality of the system changes, so do its properties; in line with theoretical predictions, the binding energy in the 2D system is independent of the interaction strength and equal to the binding energy in free space. Observation of superfluidity in the 2D layers is probably next on the agenda of simulating a cuprate.

    Phys. Rev. Lett. 108, 45302 (2012).

  5. Development

    Developmental Dynamics Uncaged

    1. Beverly A. Purnell

    Transcription factors are critical for proper gene regulation during development, but they have pleiotropic effects and dynamically regulate the spatial and temporal expression of many target genes. Because of the difficulty of studying this process using conventional methods, Shestopalov et al. devised a method to conditionally regulate the activities of several transcription factors in optically transparent zebrafish embryos. Embryos were injected with caged morpholinos targeting specific transcription factors: The RNA-targeting morpholino's repressive function is blocked initially, but exposure to UV or two-photon infrared light at specific developmental stages in specific cell populations cleaves a linker that then allows the morpholinos to block transcription factor function. Cells were then isolated and subjected to microarray analysis to determine the dynamic transcriptomes during development. As a proof of principle, the authors applied this technology to understand the activities of the No-tail transcription factor (Ntla) in axial tissues at different developmental stages.

    Nat. Chem. Biol. 8, 10.1038/nchembio.772 (2012).

  6. Chemistry

    More Mercury for the Money

    1. Jake Yeston

    Amalgam formation between silver and mercury has long been exploited on behalf of the silver, whether in facilitation of mining the precious metal, shaping it into jewelry, or embedding it in decayed teeth. More recently, however, there's been something of a role reversal under way, as silver particles are applied to the removal of toxic mercury contaminants from water sources. Katok et al. have explored the impact of silver particle size on the nature and efficiency of this process. Bulk metallic silver is known to reduce mercuric ions, with concomitant release of silver ions in a 1:2 stoichiometry. Using a range of sensitive analytical techniques, the authors found that very small (∼11-nm-diameter) silver particles supported on a reduced silica substrate removed mercuric ions from aqueous solution in a ratio exceeding 1:1. The mechanism underlying this hyperstoichiometric process remains somewhat uncertain, as does the precise lattice structure of the Hg-Ag composite produced. The authors posit a catalytic role for silver ions that may be readsorbed and reduced back to the elemental state by counterions in the solution.

    Angew. Chem. Int. Ed. 51, 10.1002/anie.201106776 (2012).

  7. Engineering

    Calling All Plumbers

    1. Nicholas S. Wigginton

    Societal water infrastructure is in dire need of rebuilding and modernization in consideration of economic as well as human safety concerns (see Caldwell, Editorial, Science, 21 October 2011). For example, leaky pipes result in the loss of 7 billion gallons of clean, treated drinking water every day in the United States alone. Water distribution networks are a hodgepodge of aging original pipes, replacement pipes, and pipes made from new materials; moreover, external pressures change over time. It is therefore difficult to predict when a system—let alone an individual pipe—will fail. Malm et al compared two statistical models of future replacement rates in Gothenburg, Sweden, based on historical data: one that includes over 100 years of data from city archives and water utility reports, the other based on a more detailed 15-year modern record. The long-term historical model more accurately predicts some factors, including the percentage of original pipes remaining in the network; however, in the absence of archived data, service life predicted using the shorter data set was still satisfactory. Overall, system replacement needs are largely reflective of how frequently pipe rehabilitation occurred in the past, and the reasons for replacement (e.g., pipe failure versus city expansion).

    Water Res. 10.1016/j.watres.2012.01.036 (2012).

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