Editors' Choice

Science  16 Jul 2010:
Vol. 329, Issue 5989, pp. 258
  1. Biotechnology

    Harnessing Commensals

    1. Barbara R. Jasny

    Our gastrointestinal tracts contain a variety of commensal bacteria that digest our food, kill harmful microorganisms, and help us function. Investigators are beginning to engineer such bacteria to make them even more beneficial. Duan and March have augmented a signaling pathway that enables a model probiotic bacterium, Escherichia coli Nissle 1917 (Nissle), to ward off cholera. The pathogenic bacterium Vibrio cholerae contains a signaling pathway that is sensitive to secreted autoinducers whose environmental concentration increases as the population density increases. At high cell densities, these autoinducers inhibit the expression of virulence genes (for cholera toxin and the intestinal attachment pilus). The authors transformed Nissle with a construct containing the gene cqsA, which is required for synthesis of the autoinducer. When infant mice were fed with transformed Nissle 8 hours before challenge with V. cholerae, 92% survived. Protection was less at shorter pretreatment times and at lower doses of transformed bacteria and was associated with a decrease in the numbers of V. cholerae in the intestines of infected mice. Although much further work needs to be done, the authors speculate that this might be an important preventive approach in regions where natural disaster increases the probability of an outbreak or even as part of the diet in impoverished areas.

    Proc. Natl. Acad. Sci. U.S.A. 107, 11260 (2010).

  2. Geochemistry

    Ore Origins

    1. Nicholas S. Wigginton

    Major mining operations of porphyry-type ore deposits—emplaced by hot magma that melted and mixed with continental crust—provide a major source of the world's supply of copper. One of the largest copper mines in operation is the 100-year-old open-pit Bingham Canyon Mine in the western United States. By measuring the lead isotope signature of tiny fluid bubbles trapped within minerals adjacent to the copper ore, Pettke et al. suggest that the Bingham Canyon deposits originate from some of the first crust formed on the primitive Earth. In this model, metal-rich fluid emerged and concentrated ∼1.8 billion years ago in the mantle after the ancient crust subducted below what is now North America. The deposits further evolved ∼37 million years ago when partial melting of the mantle underneath North America occurred during the formation of the Basin and Range province. Because this model does not require metal enrichment to occur contemporaneously with subduction processes (the generally accepted formation mechanism), additional quantities of ore-grade metals may exist in locations not typically considered favorable for metal exploration or mining.

    Earth Planet. Sci. Lett. 10.1016/j.epsl.2010.05.007 (2010).

  3. Applied Physics

    Optical Wireless

    1. Ian S. Osborne

    Numerous homes and offices are kitted out with wireless communication systems, with many components now capable of sharing a single or coupled set of routers and access points to the internet. Radio-based wireless is affected by interference, tight regulation over which bands of the frequency spectrum can be used, and technological limitations on the bandwidth and information transfer rates that be attained. As the number of added components increases, however, the first thing to give is download speed. Van Acoleyen et al. show that optical wireless communication, in which very high bandwidth and rates of transmission are available, may provide a solution. They have designed a two-dimensional optical phased array antenna that is based on the silicon-on-insulator platform used extensively in the optoelectronics industry. The incoming optical information, which can be fed in by an optic fiber, is split and directed across an array of focusing gratings by a series of patterned on-chip waveguides. The light from the gratings can be beamed off-chip at an adjustable angle by tuning the input wavelength, and can then be captured and read out some distance away, providing the basis for an optical wireless communication technology.

    Opt. Express 18, 13655 (2010).

  4. Ecology

    Driving Diversity Underground

    1. Andrew M. Sugden

    An experimental study of hay meadows in central Germany shows that the species richness of the plant community affects the impact that invertebrate herbivores exert on the vegetation. Using insecticide and molluscicide to exclude herbivores in plots of widely differing plant species diversity and productivity in a 5-year program, Stein et al. were able to confirm theoretical predictions about the relationship between diversity and herbivore effects. The exclusion of herbivores led to alterations in the composition of the plant community and also to reduced diversity; belowground herbivores had a greater impact on the community composition than their aboveground counterparts. Biomass and productivity, on the other hand, showed no clear patterns of change, suggesting that the effects of herbivore removal and diversity were not artefacts caused by increased soil fertility. These findings add to the growing body of evidence showing intricate relationships between biodiversity and ecosystem function.

    Ecology 91, 1639 (2010).

  5. Biomedicine

    Multiple Causes

    1. Kristen L. Mueller
    CREDIT: CADWELL ET AL., CELL 141, 1135 (2010)

    Complex diseases, like the inflammatory bowel condition Crohn's disease, are thought to arise from a combination of genetic and environmental factors. This two-hit pathway to disease development would explain why a genetic susceptibility allele for Crohn's disease, the autophagy gene ATG16L1, is present at approximately 50% frequency in populations of European descent, yet the incidence of Crohn's disease in these populations is quite rare. Cadwell et al. provide evidence that in mice, virus infection can interact with susceptibility genes to promote a Crohn's disease-like pathology. Mice hypomorphic for Atg16L1 and housed in an enhanced-barrier facility exhibited intestinal pathology only when infected with a persistent strain of mouse norovirus, an RNA virus that causes gastroenteritis. When mice were treated with a compound that induces intestinal injury, Atg16L1-hypomorphic virus-infected mice developed pathology (thickening of the muscularis propria and submucosal fibrosis) that resembled what is seen in Crohn's disease patients, whereas uninfected mice that expressed the hypomorphic allele did not develop Crohn's disease-like pathology, nor did virus-infected wild-type mice. Thus, an interaction between a virus and a susceptibility gene, in the presence of additional environmental factors, can determine host response phenotypes in inflammatory disease.

    Cell 141, 1135 (2010).

  6. Education

    Learning Pays Off

    1. Melissa McCartney

    The current trend in education is to focus on testing. Are potentially gifted scientists being weeded out by graduate schools' reliance on standardized assessments and grades as a measure of scientific prospects? Hazari et al. led a second round of Project Crossover, a study designed to examine the transition from graduate student to independent researcher in chemistry and physics, and developed a 145-question survey to assess individuals' goal orientation. Respondents were asked to indicate from a list of 20 options what had been the two most important factors in their decision to attend graduate school. Respondents identifying “received good grades in science” and “received a fellowship” as factors influencing their decision were classified as performance-oriented, whereas those responding with “enjoyed thinking about science” were classified as learning-oriented. Learning-oriented respondents proved significantly more successful in attaining grant funding and primary author publications than the average respondent. No significant effects were seen for performance-oriented individuals in this domain. These results suggest that nurturing the personal engagement of students is something to be considered seriously by science educators at all levels.

    Phys. Rev. ST Phys. Educ. Res. 6, 10107 (2010).

  7. Psychology

    Dark Chocolate

    1. Gilbert Chin

    Doing nothing often seems harder than doing something, even if that something is effortful and serves no apparent purpose. Hsee et al. demonstrate how little is needed to motivate students to take a 15-minute walk to drop off a survey instead of waiting in a room and dropping off the survey next door. Offering them a choice of milk versus dark chocolates at the two locations increased the percentage of ambulatory students from a third to more than half. Furthermore, in the group of subjects who were offered the same kind of chocolate at both locations (and thus could not justify the trip on the basis of preferring the faraway chocolate) the few who walked were happier than the many who waited. Finally, when students were obligated to make the short journey, they were happier being active for those 15 minutes rather than remaining idle. Hence, in the absence of constructive goals there still seems to be a happy preference for busyness.

    Psychol. Sci. 21, 10.1177/0956797610374738 (2010).