GENES & CELLS
SARS virus may trace back to bats
Chinese horseshoe bats carry two viruses that are closely related to the corona‐virus that causes severe acute respiratory syndrome, or SARS, in people. The discovery, reported October 30 in Nature, provides the strongest evidence yet that SARS originated in bats. The spread of SARS in 2002–2003 caused a pandemic that sickened more than 8,000 people and killed 774. Scientists have identified several SARS‐like coronaviruses in bats in China, Europe and Africa and have proposed that the animals may have spread the virus to humans. But there's been no convincing data to support the idea. In the new study, Xing‐Yi Ge of the Wuhan Institute of Virology in China and colleagues analyzed the genomes of the newly identified bat coronaviruses. The results show that these viruses are more closely related to the SARS virus than to other SARS‐like viruses previously identified in bats. The new viruses can also invade cells using the same human cell receptor protein that SARS uses. — Ashley Yeager
Antibody treatment shows progress against HIV
Antibodies that latch onto viral proteins can suppress HIV‐like disease in rhesus macaques for weeks or even months, researchers report October 30 in two studies in Nature. Such antibodies, patterned after ones made in rare people who can keep HIV infection in check, might someday benefit other patients chronically infected with HIV, say the research teams. The antibodies are broadly neutralizing, meaning that they can hit diverse forms of the virus. That makes them more potent than antibodies identified in earlier studies. The scientists used monkeys infected with a virus containing portions of the HIV and simian immunodeficiency viral genomes. The hybrid has the protein shell of HIV, which it uses to enter cells and cause disease. A cocktail injection of multiple kinds of antibodies dramatically lowered blood concentrations of the virus in the monkeys. The virus later rebounded, but since the antibodies attack the virus differently than HIV drugs do, a combination of the therapies might thwart the virus better than standard treatment does. — Nathan Seppa
EARTH & ENVIRONMENT
Mercury pollution to linger in California for 10,000 years
California's gold rush ended more than a century ago, but the contamination it caused will last thousands of years, a new analysis shows. Some hydraulic gold mining processes use the toxic metal mercury to separate gold from gravel. In the mid‐1800s, gold mining released more than a cubic kilometer of mercury‐laden sediments into Northern California's Sierra Nevada foothills. The sediments fanned out and inundated rivers that flow into the San Francisco Bay. Researchers estimate that 90 percent of the mercury is still trapped in the sediments. To understand how flooding and erosion may trigger future releases of the metal, researchers led by Michael Bliss Singer of the University of St. Andrews in Scotland measured mercury in sediments at 105 locations upstream of the bay. Drawing on historical flood data to predict sediment flow, the team reports October 28 in the Proceedings of the National Academy of Sciences that the mining sediments will continue to release mercury into waterways over at least the next 10,000 years. These flood‐driven discharges might pose contamination risks for people living in the region. — Jessica Shugart
ATOM & COSMOS
Milky Way home to billions of potentially habitable planets
The galaxy contains billions of potentially habitable Earth‐sized planets, according to even the most conservative estimate using data from NASA's Kepler space telescope. Although a mechanical failure recently put the telescope out of commission (SN: 6/15/13, p. 10), Kepler's census of planets orbiting roughly 170,000 stars is enabling astronomers to predict how common planets similar to Earth are across the galaxy. The authors of a study published November 4 in the Proceedings of the National Academy of Sciences conclude that 14 to 30 percent of stars similar in mass and temperature to the sun host a possibly habitable planet. Such planets orbit in a star's habitable zone, a temperate region where liquid surface water could exist, and have diameters at least as large as Earth's but no more than twice that. The estimate comes from identifying, and then extrapolating from, suitable worlds around more than 42,000 stars. The estimate is rough: If applied to the solar system, the researchers' definition of habitable zone would include the orbits of Venus and Mars, planets that are certainly not Earthlike (though they may have been in the past). Using tighter constraints, the researchers estimate that 4 to 8 percent of sunlike stars host an Earth‐sized world with a 200‐ to 400‐day orbit. Still, even 4 percent would yield a galactic population of more than a billion potentially habitable Earth‐sized planets. — Andrew Grant