 This month in Science Roundup:
Sponsored by:
  Spill ScienceThe Deepwater Horizon blowout in the Gulf of Mexico is the largest offshore oil spill in history. Both the depth and magnitude of the event pose challenges to assessing the biological effects and the expected fate of the spilled oil. The first peer-reviewed studies of the spill -- published online, ahead-of-print in Science Express this month -- now offer some details about the scope of the subsurface oil plume and its impact on marine microbes. --Camilli et al. (19 Aug 2010) used an array of instruments on both a cable-lowered water sampler and an autonomous underwater vehicle to survey the water around the BP well (see the related ScienceNOW story by R.A. Kerr). Their findings indicate the presence of a continuous hydrocarbon plume more than 35 km in length, at approximately 1100 m depth, that persisted for months. Samples collected within the plume contained more than 50 micrograms per liter (about 0.05 parts per million) of petroleum compounds, and the researchers suggest that dissolved oxygen concentrations indicate minimal hydrocarbon degradation by resident microbes (listen to the related podcast interview with study authors Rich Camilli and Chris Reddy). --Hazen et al. (24 Aug 2010) investigated the impact of the subsurface oil plume on the marine microbes residing in the plume and the rates of hydrocarbon biodegradation in deepwater samples collected from two ships between 25 May and 2 June. Contrary to the indication of Camilli et al., the team found the plume to be enriched in cold-loving bacteria that are closely related to known petroleum-degraders, and also identified hydrocarbon-degrading genes that coincided with the concentration of various oil contaminants. Moreover, these microbes appear to be degrading hydrocarbon faster than expected, suggesting that the potential for intrinsic bioremediation of the oil plume exists deep in the water column (see the related ScienceNOW story by K. Minogue). Keep tabs on Science's research, news, and commentary on the oil spill situation at www.sciencemag.org//hottopics/oilspill/ . Toward Faster-Acting Antidepressants Depression is a common, often-disabling illness that afflicts millions of people worldwide. Most antidepressant drugs now in clinical use take weeks or months to produce a therapeutic effect, but recent studies have shown that a single, low dose of ketamine -- a drug that blocks a particular type of receptor for the excitatory neurotransmitter glutamate -- can generate an antidepressant response within hours that lasts for up to a week, and works in patients who are resistant to traditional antidepressants. In a Report in the 20 Aug 2010 Science, Li et al. investigated the mechanism behind the rapid action of ketamine. The researchers found that in the rat prefrontal cortex, ketamine activates the mammalian target of rapamycin (mTOR) pathway -- a signaling pathway involved in the control of protein synthesis and implicated in learning and memory. This pathway activation leads to increased expression of synaptic signaling proteins and increases the number of connections between neurons -- the opposite of the effects caused by chronic stress and depression (listen to the related podcast interview with senior author Ron Duman). The team also showed that inhibiting the mTOR pathway prevents ketamine from stimulating the formation of new synapses and blocks its antidepressant-like behavioral effects. As noted in an accompanying Perspective by J.F. Cryan and O.F. O'Leary "these findings suggest that the rapid activation of mTOR-mediated signaling pathways may be an important and novel strategy for the rational design of fast-acting antidepressants."  Scaling Up Alternative EnergySpecial Section The end of the age of fossil fuels may be in sight, but what comes after is still a bit of a blur. In a special section of the 13 Aug 2010 issue, Science explored worldwide efforts to develop clean, renewable alternatives to fossil fuels and some of the technical, political, and economic challenges associated with scaling them up. News stories discussed energy's tricky tradeoffs, an ambitious effort to move solar electricity across the Mediterranean Sea, the unfulfilled promise of cellulosic ethanol, and growing opposition to wind turbine development. Three Perspectives took an in-depth look at how researchers hope to scale up biofuels development, and a Review discussed a two-stage approach for expanding nuclear power generation. Elsewhere in the magazine, an Editorial highlighted the policy changes needed to end the U.S. national addiction to oil, a Policy Forum focused on the social aspects of nuclear power revival, and a Perspective discussed efforts to concentrate solar electricity and fuel. Finally, a special all-energy podcast featured conversations about making the next energy transition, nuclear waste disposal, and biofuel crops that won't compete for arable land. Pulsar Discovery by Volunteer Computing Pulsars -- dense, rapidly rotating stars that form when massive stars run out of fuel and contract under their own gravity -- emit regular pulses of radio waves as they spin. Astronomers can spend years analyzing signals from radio telescopes to identify a new pulsar, but in a study published online, ahead-of-print, on 12 Aug 2010, Knispel et al. reported that a distributed computing project that harnesses the power of otherwise idle computers has made an interesting pulsar discovery of its own. Einstein@Home, a so-called citizen science project, aggregates the computer power of hundreds of thousands of volunteers from 192 countries to "mine" large astronomical data sets. Now, three participants whose computers analyzed radio survey data taken in February 2007 at the Arecibo Observatory in Puerto Rico are being credited with the discovery of PSR J2007+2722, a fast-spinning pulsar that rotates once every 0.0245 seconds (see the related ScienceNOW story by S. Reed). The pulsar appears to belong to a rare class known as disrupted recycled pulsars, which form by cannibalizing matter from a companion star that has since been expelled from a binary system. The discovery provides hope that the massive computing power provided by volunteers will lead to further discoveries in astronomy and other data-driven fields in the future.  Bats and DiseaseBats are known to host a variety of pathogens that pose threats to bats themselves, as well as to other wildlife and to humans. Two bat studies in the 6 Aug 2010 issue offered new insights into the complex dynamics of cross-species transmission of rabies virus (bats being the most common source of human rabies infections), and the impact of an emerging fungal disease on regional bat populations (see the Perspective by P. Daszak). Streiker et al. used decades of surveillance data on bat rabies, virus sequence data, and information on bat ecology to investigate the likelihood of cross-species virus transmission. They found that phylogenetic closeness is an important factor in predicting the probability of cross-species transmission, more so than physical proximity between species or the intrinsic mutability of the virus. Frick et al. reported that white-nose syndrome -- a fungal infection that causes hibernating bats to become restless and exhaust their vital fat reserves -- is causing unprecedented mortality among bats in eastern North America (see the related ScienceNOW story by E. Stokstad). Population data collected over the last 30 years, combined with population simulations, indicate that this collapse could lead to regional extinction of the little brown myotis, a once widespread and common bat species, within 16 years -- potentially hurting agriculture and forests (listen to the podcast interview with lead author Winifred Frick). Optimally Interacting Minds When it comes to decision-making, are two heads really better than one? In a Report in the 27 Aug 2010 Science, Bahrami et al. tested the merits of collaborative decision-making, and found that the decision of a group can indeed be more accurate than the decision made by an individual -- but only under certain conditions. The team performed an experiment in which pairs of participants were asked to identify faint targets in briefly viewed visual displays. They found that among pairs of participants with similar visual acuity, two heads were definitely better than one, provided that the individuals were able to communicate freely not only about what they saw, but also about their degree of confidence in their observations. For pairs of participants with very different visual sensitivities, however, two heads collaborating resulted in worse decisions than those by the individual with better visual acuity alone. The findings demonstrate that human beings communicate some measure of certainty in their decisions when they are free to discuss their perceptions, and have direct bearing on studies in social psychology that have discovered numerous situations in which groups fail to do better than their individuals. An accompanying Perspective by M.O. Ernst highlighted the study.  Anti-HIV AntibodiesDeveloping a vaccine against HIV remains a top global health priority. However, the virus has rapidly evolved a daunting degree of diversity, posing a considerable challenge for vaccine development. One strategy is to isolate broadly neutralizing antibodies from infected individuals and then attempt to elicit the same antibody response through vaccination. Two studies in the 13 Aug 2010 Science (published online 8 Jul) reported important developments toward this goal. Wu et al. used a novel selection strategy to identify three potent and broadly neutralizing antibodies from an HIV-1-infected individual. These antibodies are specific for the site in the viral envelope protein gp120 that binds to CD4, the receptor used by HIV to dock onto cells. One of the antibodies, VRC01, neutralizes about 90% of the nearly 200 HIV-1 strains that were tested. Zhou et al. analyzed the crystal structure of VRC01 in complex with an HIV-1 gp120 molecule and found that this antibody partially mimics the CD4 interaction with gp120, focusing its binding onto the site of initial CD4 attachment, which is conformationally invariant between viral strains. An accompanying Perspective by D.R. Burton and R.A. Weiss highlighted the findings. Improving Earth Models Mantle convection and associated plate tectonics are principal controls on the thermal and geological evolution of the Earth. Despite the central importance of plate dynamics, there are fundamental uncertainties about the forces resisting and driving plate motions, due in large part to the computational challenge of achieving large-scale, high-resolution simulations. In a Research Article in the 27 Aug 2010 Science, Stadler et al. described a new method for modeling Earth's geophysical processes that provides a much more refined picture of how these processes are shaping the planet's surface and interior. By using large parallel supercomputers, the researchers improved upon a commonly used method in engineering and physics called adaptive mesh refinement to increase the resolution of global geodynamic models to the scale of a single kilometer. In doing so, they revealed unexpected insights into localized processes, such as subduction zone mechanics, thermal anomalies in the lower mantle, and the speed of movement of oceanic plates. An accompanying Perspective by T. Becker discussed the findings in more detail.  Nanoantennas for Quantum DotsThe atom-like features of quantum dots -- the discrete energy levels and subsequent emission of light at discrete wavelengths -- make them attractive building blocks for optoelectronic circuits and optical communication. However, the light emitted from these tiny semiconductors tends to shoot off in every direction, limiting applications that require accurate transmission between sender and receiver. As described in a Report in the 20 Aug 2010 Science, Curto et al. have now designed a nanometer-scale riff on a familiar type of television and radio antenna, fashioned from gold, that allows visible radiation -- which has wavelengths of hundreds of nanometers -- to couple into a semiconductor quantum dot only a few nanometers in diameter, and also direct the emission. In the team's setup, a quantum dot is placed in the near field of a gold antenna so that it drives the resonant feed element of the antenna. The resulting quantum-dot luminescence is strongly polarized and highly directed into a narrow forward angular cone -- and the directionality of the quantum dot can be controlled by tuning the antenna dimensions. A Perspective by H. Giessen and M. Lippitz discussed how this technology could lead to improvements in quantum communication and computing. Parental Influences Genomic imprinting is a form of epigenetic regulation (chemical modification of DNA) that results in the preferential expression of the paternally or maternally inherited copy (allele) of certain genes. Two studies by Gregg et al. in the 6 Aug 2010 Science (published online 8 Jul) shed new light on the scale and complexity of genomic imprinting in the mammalian brain. As described in a Research Article and companion Report, the researchers used a genome-wide approach to characterize the repertoire of genes showing imprinting in the mouse embryonic and adult brain and uncovered over 1300 loci showing maternal or paternal bias in expression. They observed a preferential maternal contribution to gene expression in the developing brain and a major paternal contribution in the adult brain, but also identified parental biases specific to certain brain areas and even to the sex of the individual. In the hypothalamus for example, sex-specific imprinted genes were mostly found in females, which suggests parental influence over the hypothalamic function of daughters. An accompanying Perspective by L.S. Wilkinson highlighted the studies, which raise a number of new questions about the underlying molecular mechanisms controlling parental gene expression bias and the extent to which the data obtained in mice are relevant to humans. In Science Signaling
|
