Findings

Science  10 Feb 2012:
Vol. 335, Issue 6069, pp. 642
  1. Study Fails to Find Arsenic in Microbial DNA

    The debate over whether a bacterium can incorporate arsenic into its DNA flared up again last week, with the posting of a paper refuting the idea on arXiv, an electronic preprint archive primarily used by physical scientists. The December 2010 report online in Science describing a microbe that grew in arsenic and seemed to incorporate the toxic element into its biomolecules had already elicited eight critical technical comments (Science, 3 June 2011, p. 1149).

    Now one vocal critic, Rosemary Redfield, a microbiologist at the University of British Columbia, Vancouver, in Canada, and colleagues at Princeton University have grown the bacterium in the presence of arsenic, mimicking the original paper's methodology. After stringent purification steps, Redfield and her colleagues tested the bacterium's DNA for arsenic using liquid chromatography mass spectrometry. Contrary to the original report, they found that arsenic did not stimulate growth of the microbe, and they saw no evidence of its uptake in the microbe's genetic material. Now, says Redfield, “The burden of proof is back on the authors.” http://scim.ag/Redfield

  2. Telltale Isotopes Hint at North Korea Weapons Test

    In mid-May 2010, monitoring stations near North Korea belonging to the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) detected radionuclides in the air, suggesting a nuclear weapons test. There were no seismic signals of an explosion, however, and the ratio of nuclides did not fit the usual pattern for a weapons test. “It was a mystery for most in the field,” says Lars-Erik De Geer of the Swedish Defense Research Agency.

    De Geer suggests an explanation in an upcoming issue of Science & Global Security. North Korea may have carried out a low-yield underground test on 11 May that leaked some radionuclides immediately and more on two later occasions. An excess of xenon-133 suggests the test cavity was contaminated by an earlier blast, hinted at in a government report that mentions a nuclear “success” on 15 April. The 11 May blast, which may have been too small to be picked up seismically, appeared to use uranium-235 rather than plutonium-239.

    Richard Garwin of the Federation of American Scientists says other, simpler explanations could account for the radionuclides detected, such as reprocessing spent nuclear fuel to make isotopes for medical imaging. “There's a big burden of proof to show it's not reprocessing,” he says.

  3. New Malaria Death Toll Disputed

    A new attempt to calculate the global number of malaria deaths claims that 1.2 million people died of the disease in 2010, twice as many as the estimates from the World Health Organization (WHO). But many experts question the new figures, especially the higher death toll for adults.

    Lifesaver.

    Treated bed nets have reduced malaria mortality.

    CREDIT: PHILONG SOVAN/XINHUA/LANDOV

    Calculating the number of malaria deaths is difficult because public health records in the hardest-hit areas are scarce. Christopher Murray of the University of Washington, Seattle, and his colleagues combed through data on causes of death between 1980 and 2010 in the 105 countries with malaria transmission. They then developed computer models that included factors like drug resistance and weather patterns to estimate the worldwide toll.

    Their report in the 4 February issue of The Lancet concludes that 435,000 Africans over age 5 died of malaria in 2010—eight times WHO's number. That's too high, says malaria epidemiologist Robert Snow of the Kenya Medical Research Institute in Nairobi; severe malaria is rare in adults, he says, because exposure to the disease helps build partial immunity. Malaria is a common misdiagnosis, he adds, so records can be misleading. Snow hopes the debate will highlight the need for better surveillance. “We need to be honest … in saying we don't know,” he says. “This is another example of guessing.”

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