Editors' Choice

Science  20 Mar 2015:
Vol. 347, Issue 6228, pp. 1326
  1. Electrochemistry

    Silver's salty twist on water splitting

    1. Jake Yeston

    When plants split water during photosynthesis, they expel oxygen as a by-product. Ironically, it's this oxygen-generating step that's also proving the most difficult to optimize in artificial photosynthetic schemes, where the practical goal is simply to release the oxygen while accumulating hydrogen for fuel. Du et al. explore an alternative scheme, whereby the electrons to make the hydrogen come from chloride ions—already abundant in seawater—instead of other water molecules. Specifically, they show that dissolved silver ions act as efficient electrocatalysts for chloride oxidation, provided that the chloride is present at a high enough concentration to form (AgCl2) and (AgCl3)2− ions, both of which are more soluble and more reactive than AgCl.

    J. Am. Chem. Soc. 10.1021/jacs.5b00037 (2015).

  2. Paleoecology

    Plant community structure through time

    1. Andrew M. Sugden

    A wide variety of biotic and abiotic factors controls the abundance and biomass of plant species in ecological communities over time. Although challenging to tease apart, doing so may help scientists to better understand the effects of climate change on various ecosystems. Jeffers et al. combined analysis of fossil pollen records, isotopic analysis, paleotemperature reconstruction, and population modeling to study the factors that influenced the structure of tree communities in Scotland 12,700 to 5200 years ago. For most of the species in the community, interactions between plants controlled their abundance, more than soil nitrogen availability or growing-season temperature.

    J. Ecol. 103, 459 (2015).

  3. Nosocomial Infection

    No clear bacterial culprit for NEC

    1. Kristen L. Mueller

    Pre-term infants are especially susceptible to necrotizing enterocolitis

    PHOTO: BLEND IMAGES - ERPRODUCTIONS LTD/GETTY IMAGES

    Of all the obstacles faced by premature infants, necrotizing enterocolitis (NEC) is a particularly scary one. The disease kills developing intestinal tissues and sometimes the infants themselves. Scientists still don't know what causes NEC, but because the disease responds to antibiotics, they suspect that a contagious bacterium may be to blame. Raveh-Sadka et al. used a metagenomics approach to identify the microbes present in premature hospitalized infants during a NEC outbreak. They found that these babies shared very few bacterial strains, suggesting that no single bacterium caused the outbreak. Although this indicates that hospitals have good barriers in place to stop the spread of dangerous bacteria in these fragile infants, the cause of NEC remains a mystery.

    eLife 4, e05477 (2015).

  4. Aging

    DNA mutations do not age yeast

    1. L. Bryan Ray

    The molecular basis of aging—just what it is that wears out and causes the functional decline of an aged cell or organism—remains unclear. In hope of better understanding this, Kaya et al. monitored individual yeast cells and sequenced their DNA to test whether accumulated DNA mutations are a cause of replicative aging in yeast. The number of daughter cells produced before a mother yeast cell dies defines the replicative life span of the mother cell. But the cells accumulated only 0.4 mutations over the life span of an average cell. Thus, at least in yeast, DNA mutations do not seem to cause aging.

    Aging Cell 10.1111/acel.12290 (2015).

  5. Climate Change

    An underground route to the atmosphere

    1. H. Jesse Smith

    Arctic lakes, like this one in eastern Greenland, could emit more methane due to climate warming

    PHOTO: PIERRE VERNAY / POLAR LYS / SCIENCE SOURCE

    As climate changes and temperatures rise, so do concerns that methane emissions from the Arctic may increase, because methane is a powerful greenhouse gas. Arctic lakes are known to be an important source of methane, but the origins of their emissions are not well understood. Paytan et al. investigated Toolik Lake, Alaska, in order to determine what fraction of the methane it emits is from microbial activity within the lake versus how much is transported into the lake by groundwater. They find that groundwater supplies a major fraction of the lake's methane, which implies that if Arctic warming causes this type of groundwater flow to increase, then the methane flux from lakes to the atmosphere could grow as well.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1417392112 (2015)

  6. Noncoding RNA

    Circular RNA transcriptional circuits

    1. Guy Riddihough

    Scientists first observed circular RNAs, a type of noncoding RNA, in mammalian cells over 30 years ago but are only now beginning to elucidate their functions. Circular RNAs generally contain either exclusively gene exon or gene intron sequences. Li et al. now describe an unusual class of circular RNAs in human cells that contain both exon and intron sequences. These RNAs localized to the nucleus, where they bound to protein components of the transcription machinery and RNA components of the splicing machinery. By binding to the promoters of their own genes, they fine-tuned transcriptional activation of these genes.

    Nat. Struct. Mol. Biol. 10.1038/nsmb.2959 (2015).

  7. Infectious Disease

    A virulence factor comes under scrutiny

    1. Julia Fahrenkamp-Uppenbrink

    The human pathogen Streptococcus pyogenes produces streptolysin S (SLS), a virulence factor that helps the pathogen to invade host cells and to evade recognition by the host immune system. Maxson et al. show that the HIV protease inhibitor nelfinavir blocks a key step during SLS biosynthesis. The authors synthesize and test nelfinavir analogs to study the role of the SagE protein in the SLS biosynthesis pathway. Use of these analogs to inhibit SLS production will help to elucidate how SLS contributes to S. pyogenes virulence and may even lead to novel treatment strategies.

    ACS Chem. Biol. 10.1021/cb500843r (2015)

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