This Week in Science

Science  21 Jan 2011:
Vol. 331, Issue 6015, pp. 259
  1. Not Purely Decorative

      CREDIT: FABRIZIO SERGIO

      Phenotypic signals such as plumage patches are common among animals and indicate reproductive quality. Animals are also able to advertise their quality by building structures from materials gathered from their environment. In a comprehensive study of nest decorating behavior in black kites, Sergio et al. (p. 327) found that birds that placed the most white plastic in their nest not only produced more offspring but also had better territories and were better at defending them in aggressive encounters. The amount of decoration placed decreased with age and, surprisingly, lower-quality individuals do not “cheat,” going out of their way to remove material experimentally placed in their nests.

    1. Disease on the Run

        Migratory animals can spread infections—including human pathogens such as West Nile, avian influenza, Hendra, and Ebola viruses—to new geographic areas. The physiological stress of migration can lead to immunocompromise and consequent high rates of infection, but, in other contexts, migration can allow escape from parasites. Altizer et al. (p. 296) review the ecological, immunological, and evolutionary mechanisms by which migration can alter the spatial spread, prevalence, and severity of infectious disease in animal populations.

      1. Making Neurons

          Transcription factors are essential drivers of specific terminal differentiation programs. However, the ability of transcription factors to drive differentiation programs upon ectopic expression is often restricted by cellular context, which hinders our ability to generate cell types at will. Using a genetic screening approach in the nematode Caenorhabditis elegans, Tursun et al. (p. 304, published online 9 December; see the Perspective by Strome) found that removal of a chromatin factor allowed transcription factors to reprogram germ cells directly into specific neuron types, in a relatively fast and efficient manner.

        1. Methane Oxidation at Deepwater

            The Deepwater Horizon blowout in June 2010 in the Gulf of Mexico has provided a site for studying a number of marine processes in situ that would not otherwise have been possible. The release of massive amounts of methane from the wellhead resembles rare but potentially dangerous massive outgassing events from natural seeps or gas hydrates along the ocean floor. Kessler et al. (p. 312, published online 6 January) surveyed waters during the leak and after the wellhead was sealed and found that bacteria degraded all of the methane released from the well within ∼120 days of the initial blowout—and within only ∼40 days once the well was sealed. The presence of low oxygen anomalies in the water column and a shifted bacterial community structure toward methanotrophy suggests that the ecological response to such large events can be faster and more efficient than anticipated.

          1. Processing the Moon's Core

              CREDIT: WEBER ET AL.

              The Apollo Passive Seismic Experiment measured lunar ground motion until the mid-1970s. Since then, various efforts have attempted to extract all possible information about the interior of the Moon from this unique data set. Recent computational and methodological advances suggest that reprocessing the aging seismic data may provide previously inaccessible information buried within. To that end, Weber et al. (p. 309, published online 6 January) reanalyzed the Apollo data using a method typically reserved for processing seismic array data on Earth. The data indicate that the lunar core, like Earth's, consists of a solid inner core and molten outer core. Unlike Earth, however, the Moon also has a thick partial melt layer resting above the outer core.

            1. Spinning in Water

                Nearly a century ago, Stern and Gerlach demonstrated that the electrons bound to atoms have an unusual binary property, termed spin, which causes their deflection in one of two directions on passage through uneven magnetic fields. Certain nuclei were soon discovered also to possess spin, leading to the development of nuclear magnetic resonance spectroscopy. Kravchuk et al. (p. 319) have now used a magnetic apparatus similar to the Stern-Gerlach setup to separate the nuclear spin isomers of water. Specifically, a cold, rapid beam of water diluted in a carrier gas was sent through the magnetic field region. The ortho isomers (in which both H atoms in the H2O share the same spin orientation) were focused toward the center while the para isomers followed a divergent path, allowing their separation. The technique could also be applied to methane, showing promise for future in-depth studies on spin-pure ensembles of small molecules.

              1. His and Hers Fossils

                  Evidence of sex, let alone details of the modes of reproduction, are scarce in fossils, hampering understanding of sexual dimorphism and the life of extinct species and groups. et al. (p. 321) have discovered an indisputably female fossil pterosaur that includes an egg next to its pelvis. The fossil Darwinopterus dates to 160 million years ago and was collected from sedimentary rocks in Liaoning Province, China, and lacks a crest, indicating that crests are likely to have been characteristic of males. The egg is relatively small compared to the pterosaur body size, and its shell was not hard like those of bird eggs, but the egg was instead probably covered in parchment, more like the eggs of some other reptiles.

                1. On the Move

                    In general, as global temperatures increase, plant and animal species will shift their distributions uphill or away from equatorial latitudes to maintain their climatic niche. However, exceptions have been noted to the uphill pattern, with a minority of species showing downhill trends in their distribution. By comparing vegetation data from the 1930s with present-day data, Crimmins et al. (p. 324) show that the optimum elevations for a majority of mountain plant species in California, USA, have moved downhill by approximately 80 m, despite widespread and substantial increases in temperature during the 20th century. This seeming anomaly could be explained by linking plant species' altitudinal positions to climatic water balance. Increases in precipitation during the 20th century have outpaced increases in plants' evaporative demand owing to temperature rises and have led to increased water availability across northern California.

                  1. Immune Evasion Tactic

                      Pattern recognition receptors are critical to allow cells to sense invading viruses and initiate antiviral immune responses, but viruses deploy a myriad of tactics to avoid detection and induction of antiviral immunity. Gregory et al. (p. 330) found that Karposi's sarcoma–associated herpesvirus (KSHV), the etiological agent of several human cancers, encodes a gene (Orf63) homologous to NLRP1, a member of the nucleotide-binding domain, leucine-rich repeat (NLR) containing a family of pattern recognition receptors. Orf63 interacted with NLRP1, prevented its oligomerization, and inhibited activation of downstream antiviral responses. Thus, KSHV can evade the immune response by inhibiting an important viral detection pathway in the host.

                    1. Playing the Game

                        CREDIT: WAN ET AL.

                        Experts in various cognitive fields, including board games, show superior abilities not only for the quick perception of relevant input patterns but also for the rapid generation of appropriate responses. Largely unconscious automatic, or “intuitive,” processes are essential for this superior performance. Wan et al. (p. 341) analyzed the brain activity of subjects playing shogi (Japanese chess). Compared to amateurs, professional players showed specific brain activation in the parietal lobe during rapid perception of shogi patterns. When pushed to come up with the next best move extremely quickly, the experts showed activation in the caudate nucleus. However, when the players took their time and consciously evaluated a given board pattern, brain activation was limited to the prefrontal cortex and other cortical areas in both professional and amateur players.

                      1. Living Life in the Extreme

                          Haloarchaea are commonly found tinting salt evaporation pans pink with carotenoid pigments. These prokaryotes have an array of distinctive characteristics needed to live in an extreme environment, including various molecular strategies for water retention, for example, by accumulating osmoprotectant compounds like glutamate and polyesters. Khomyakova et al. (p. 334; see the Perspective by Ensign) now describe an alternative route by which osmoprotectant storage compounds can feed into carbon assimilation. In Haloarcula morismortui, the classical citric acid and glyoxylate cycles are diverted into a methylaspartate cycle at isocitrate by acquisition of the key enzymes, glutamate mutase and methylaspartate ammonia-lyase.

                        1. Clostridium to the Rescue

                            The gastrointestinal (GI) tract is home to a diverse population of commensal bacteria that works with the immune system to protect against infection but is also critical for maintaining immune homeostasis. How specific microflora influence immune cell homeostasis in the GI tract is only beginning to be understood. Working in mice, Atarashi et al. (p. 337, published online 23 December; see the cover; see the Perspective by Barnes and Powrie) now show that indigenous Clostridium species promote the generation of regulatory T cells (Treg cells) in the colon. Germ-free mice had reduced numbers of colonic Treg cells, which were rescued by colonization with Clostridium.

                          1. Exotic Quantum Materials

                              Quantum critical transitions (QCT) occur when temperatures approach absolute zero and are caused by quantum, rather than thermal, fluctuations. In the vicinity of these transitions, materials often exhibit exotic transport properties. QCTs are usually accessed by varying an external parameter such as the pressure or the magnetic field or, alternatively, by using chemical doping to fine-tune the material into a nonstoichiometric (and thus disordered) state. Matsumoto et al. (p. 316) now achieve quantum criticality without any such tuning in the compound β-YbAlB4. Because of the mixed-valence nature of this heavy fermion material, it is likely that instead of a conventional quantum critical point, the experiments are accessing an exotic quantum critical phase.

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