Volume 454

  • No. 7208 28 August 2008

    Deep-sea sediments contain large reservoirs of carbon in the form of microbial biomass, and the dynamics of this ecosystem are only now being established. A paper in last week's Nature showed that Archaea predominate over Bacteria in an extensive sediment prokaryote community. This week Danovaro et al. report on the impact of viral infections in this ecosystem. Data from 232 sediment samples show that virus production is very high. Viral infections cause the abatement of over 80% of prokaryotic biomass production close to 100% at depths below 1,000 metres - thereby releasing huge amounts of dissolved organic carbon into the deep seas. In waters otherwise short of resources this injection of nutrients is particularly significant. Viruses therefore appear to play a major role in global biogeochemical cycles, deep-sea metabolism and overall functioning of the largest ecosystem of our biosphere. The cover graphic illustrates the battle between deep-sea viruses and bacteria, where bacteria destroyed by viruses provide food for other bacteria. [Article p. 1084; News 1038] Cover art: Mirco Tangherlini/ www.tangherlini.it

  • No. 7206 14 August 2008

    Electricity generation is responsible for a sizeable proportion of global carbon dioxide emissions. We have the technologies to generate electricity without net carbon emissions from fuel, an obvious response to the predictions of global warming, but one that has so far had little take-up on a global scale. If carbon-free electricity is to become a more practical proposition the various sources of carbon-free generation need to be scaled up to power an increasingly demanding world. In a News Feature special this week, Nature's reporters ask the big questions. First, how much carbon-free energy might ultimately be available? And second, how do the rival technologies compare. The alternatives include traditional hydroelectricity, tidal and wave power, nuclear, solar and a few others. A lot depends on how the technologies develop, but on balance, don't discount a 'solar' future. [News Feature p. 816; Editorial p. 805; www.nature.com/podcast] Cover graphic by Jay Taylor.

  • No. 7205 7 August 2008

    The electronic eye camera shown on the cover is a notable advance in optoelectronics. Even with the latest technologies it is difficult to produce a device to match the feats of imaging achieved by the human eye. Its hemispherical detector provides a wide field of view and low aberrations, using simple, single-component optics. Conventional optoelectronics materials exist only on the planar surfaces of rigid semiconductor wafers and cannot adopt spherical shapes. Now a multidisciplinary team based at the University of Illinois at Urbana-Champaign and Northwestern University, Evanston, has created an electronic eye-like camera based on single-crystalline silicon technology. Two novel fabrication steps make this possible. First, the optoelectronic circuits are ultra-thin in unusual, two-dimensionally compressible configurations; second, specially designed elastomeric elements transfer these planar layouts into hemispherical geometries. In addition to eye-like cameras, these strategies should make it possible to integrate planar device technologies onto the surfaces of complex curvilinear objects, for use in health monitoring devices, ‘smart’ prosthetics and elsewhere. [Letter p. 748; News & Views p. 703]

  • No. 7204 31 July 2008

    An 'evo-devo' study of venomous snakes has arrived at a new model for the evolution of snake fangs, a subject of some controversy. Many of the advanced snakes alive today use syringe-like fangs to inject venom into their prey. The fangs are either at the front or rear of the upper jaw, and the controversy lies in whether the two arrangements are evolutionarily related. By visualizing tooth-forming epithelium in the upper jaw of 96 snake embryos from 8 species, the study shows that 'front-fanged' and 'rear-fanged' types are strikingly similar in morphogenesis. Front fangs develop from a rear part of the upper jaw that migrates forward during development, and rear fangs from a specialized zone that stays put. The new model proposes that a posterior subregion of tooth-forming epithelium became developmentally uncoupled from the remaining dentition, allowing the posterior teeth to evolve independently in close association with the venom gland, becoming highly modified in different lineages. This developmental event could have facilitated the massive radiation of advanced snakes in the Cenozoic era, resulting in the spectacular diversity of snakes seen today.

  • No. 7202 17 July 2008

    Scanning tunnelling microscopes made it possible to image atomic-scale features on a solid-state surface. But they have limitations in terms of sample conductivity, cleanliness and data acquisition rate. An older technology, the transmission electron microscope (TEM), meanwhile evolved to be able to image individual heavy atoms. But lighter atoms remained beyond its range because of their low contrast. Enter graphene, the one-atom-thick sheet of carbon atoms packed in a dense two-dimensional honeycomb lattice. Meyer et al. show that atoms as small as carbon and even hydrogen adsorbed onto graphene can be imaged using standard TEM technology. Ultrathin graphene is an ideal support, either invisible or, if the lattice is resolved at high resolution, its contribution to the imaging signal is easily removed. This approach brings atomic resolution to biomolecules as well as to graphene itself .The cover shows hydrogen atoms (purple) on a graphene sheet (red), with a carbon atom (yellow tipped) near left centre. Yellow peaks are amorphous carbon.

  • No. 7201 10 July 2008

    The Ebola virus, one of the most feared of pathogens, causes a severe haemorrhagic fever with up to 90% human mortality. Since 1994, outbreaks of the virus have increased fourfold. Although initial vaccine trials in primates have shown promise, no vaccines or post-exposure treatments are yet available. And it is still not clear why the virus is so pathogenic or why the immune response is so weak in fatal cases. A team from The Scripps Research Institute has now determined the crystal structure of the trimeric Ebola virus glycoprotein bound to a neutralizing antibody isolated from a human survivor. The structure reveals a putative receptor-binding site sequestered in a bowl of a chalice formed by three GP1 viral attachment subunits (in shades blue in the molecular surface model on the cover), cradled by three GP2 fusion subunits (coloured white). Access to the site is restricted by a glycan cap and a protruding mucin-like domain. The antibody (in yellow) bridges the GP1 and GP2 subunits and is specific for the prefusion, viral surface conformation of GP2. [Article p. 177] Cover grapics by Christina Corbaci & Michael Pique.

  • No. 7200 3 July 2008

    On 30 August 2007 Voyager 2 began to cross the termination shock, a boundary produced by the inter-action of the Sun with the rest of the Galaxy, where the supersonic solar wind abruptly slows as it presses outward against the surrounding interstellar matter. Five Letters in this issue present the data that the probe sent back. The Voyager 2 crossings occurred about 1.5 billion kilometres closer to the Sun than those of Voyager 1, illustrating the asymmetry of the heliosphere. The results from the plasma experiment [p. 63], low-energy particle [p. 67], cosmic ray [p. 71], magnetic field [p. 75] and plasma-wave detectors [p. 77] reveal a complex and dynamic shock, reforming itself in hours rather than days. It may be decades before another probe crosses the termination shock but remote observations can now bridge the gap - as shown by Wang et al. who report measurements of energetic neutral atoms in the heliosheath from the STEREO A and B spacecraft that complement the Voyager in situ observations made at the same time [Letter p. 81]. In News & Views, Randy Jokipii puts the Voyager findings into context [p. xx]. And on page xx, historic images from the planetary phase of the Voyager mission. Meanwhile, Voyagers 1 and 2 head for interstellar space, so may still have more to tell us. Cover graphic: Henry Kline/JPL