This Week in PNAS
CHEMISTRY
Sulfur content of the warship Mary Rose
Magnus Sandström et al. analyzed the concentration and composition of sulfur compounds in the wooden timbers of the Mary Rose, Henry VIII's warship, which was sunk in 1545 and salvaged in 1982. Using methods including x-ray spectroscopy and fluorescence, the authors determined that the sulfur concentration in the hull timbers varies from 0.4 to 2.0 mass%, equivalent to ≈2 tons of sulfur in the 280-ton hull. The sulfur primarily occurred in reduced forms: organosulfur, iron sulfides, and elemental sulfur. The accumulation of organosulfur compounds in the form of high concentrations of thiols and disulfides were present in the lignin-rich parts of the wood, especially the middle lamella between cells. This finding indicates a direct reaction of bacterially produced hydrogen sulfide with the active sites in lignin, after the dissolved hydrogen sulfide penetrated the waterlogged wood. Iron, partly in sulfides, was also found in the timbers at varying concentrations, with highest levels in wood cracks and bolt holes. Sandström et al. suggest that, after removing or stabilizing these oxidizing iron species, the remaining lignin-bonded organosulfur could be prevented from forming acid in the wood, improving long-term conservation of the ship. — N.Z.
“Sulfur accumulation in the timbers of King Henry VIII's warship Mary Rose: A pathway in the sulfur cycle of conservation concern” by Magnus Sandström, Farideh Jalilehvand, Emiliana Damian, Yvonne Fors, Ulrik Gelius, Mark Jones, and Murielle Salomé (see pages 14165-14170)
ENVIRONMENTAL SCIENCES
Degassing lakes to prevent CO2 clouds
George Kling et al. report that two African lakes have the potential to release potentially deadly clouds of CO2, despite current preventive efforts, and additional degassing pipes in these lakes may be warranted. In the 1980s, Lakes Nyos and Monoun in Cameroon released clouds of CO2, killing ≈1,800 people by asphyxiation. CO2 released from magma accumulates in the bottoms of the deep, highly stratified lakes, where it can become trapped and released in a toxic cloud. Since the 1980s, each lake has been outfitted with a pipe to vent CO2. Based on 12 years of data, Kling et al. found that both lakes are being recharged with CO2 with gas saturation values of 80-90%, indicating that a single pipe in each lake is not enough to dissipate all the gas. In the next decade, each pipe is predicted to remove only ≈30% of the gas, which would reduce but not eliminate the toxic cloud risk. By modeling past and future CO2 replenishment and removal rates, the authors posit that two pipes in Lake Monoun and five pipes in Lake Nyos would remove ≈75% and 90%, respectively, of the remaining CO2 by 2010. — P.D.
“Degassing Lakes Nyos and Monoun: Defusing certain disaster” by George W. Kling, William C. Evans, Greg Tanyileke, Minoru Kusakabe, Takeshi Ohba, Yutaka Yoshida, and Joseph V. Hell (see pages 14185-14190)
APPLIED BIOLOGICAL SCIENCES
Radiation damages unirradiated tissue over long distances
Using a reconstructed 3D model of human skin tissue, Oleg Belyakov et al. demonstrate that radiation can damage or kill cells not directly exposed to the radiation but within the vicinity of exposed cells. The authors induced radiation damage in a skin model with a charged-particle microbeam, which allowed irradiation of a localized group of cells while ensuring that other cells in the tissue were untouched. They observed “bystander” responses relatively far from the site of damage, including the appearances of micronuclei up to 0.6 mm away and apoptotic cells up to 1 mm away. The average increase in occurrence compared with control tissues was 1.7-fold for micronuclei and 2.8-fold for apoptosis. The increased effects remained constant over the first several hundred micrometers, indicating that unirradiated cells responded in a binary way to a damage signal, as long as the signal remained above a threshold value. The long range of these responses implies that irradiated cells may release diffusible signals into surrounding tissue, or may activate a cell relay system. Belyakov et al. suggest that bystander effects may be important when extrapolating low-dose radiation risk estimates. — N.Z.
“Biological effects in unirradiated human tissue induced by radiation damage up to 1 mm away” by Oleg V. Belyakov, Stephen A. Mitchell, Deep Parikh, Gerhard Randers-Pehrson, Stephen A. Marino, Sally A. Amundson, Charles R. Geard, and David J. Brenner (see pages 14203-14208)
BIOCHEMISTRY
Small RNAs implicated in Staphylococcus aureus virulence
Christophe Pichon and Brice Felden have identified a number of small RNAs (sRNAs) expressed by Staphylococcus aureus that may play important roles in bacterial virulence and the evolution of antibiotic resistance. RNAs, once thought to be simply blueprints for the manufacture of proteins, are now known to be active participants in many cell functions. sRNAs are expressed in all organisms and are thought to regulate gene expression and mRNA stability. However, few have been identified in gram-positive bacteria such as S. aureus, which is resistant to a number of antibiotics. With the help of complete genome sequences of several strains of S. aureus, Pichon and Felden identified 12 sRNA transcripts expressed in this species. Using comparative genomics and microarrays, the authors found eight unique sRNAs and four transcripts predicted from sequence comparison. Seven sRNAs were found within pathogenicity islands, and expression varied among the four pathogenic S. aureus strains analyzed. — M.M.
“Small RNA genes expressed from Staphylococcus aureus genomic and pathogenicity islands with specific expression among pathogenic strains” by Christophe Pichon and Brice Felden (see pages 14249-14254)
DEVELOPMENTAL BIOLOGY
Cochaperone protein necessary for embryo implantation
Susanne Tranguch et al. report that female mice lacking the immunophilin protein FKBP52, which acts as a cochaperone for the nuclear progesterone receptor (PR), cannot support blastocyst implantation during pregnancy. In mammals, progesterone binds to PR and modulates uterine physiology by regulating genes required for implantation. Previous research has shown that the functional PR exists as a complex with heat shock proteins and cochaperones, though the contribution of the cochaperones has not been clearly understood. Tranguch et al. generated mice with targeted deletions of either FKBP52 or FKBP51, immunophilins known to complex with PR. FKBP52-null, but not FKBP51-null, female mice were shown to be infertile. Although FKBP52-null mice ovulated normally and produced sufficient amounts of progesterone, they showed no signs of blastocyst attachment to the uterus. Wild-type blastocysts transferred to pseudopregnant, FKBP52-null mice were similarly unable to implant. Progesterone binding to PR was found to be reduced nearly 2-fold in the uterine cytosol of knockout mice, compared with wild type. — F.A.
“Cochaperone immunophilin FKBP52 is critical to uterine receptivity for embryo implantation” by Susanne Tranguch, Joyce Cheung-Flynn, Takiko Daikoku, Viravan Prapapanich, Marc B. Cox, Huirong Xie, Haibin Wang, Sanjoy K. Das, David F. Smith, and Sudhansu K. Dey (see pages 14326-14331)
Figures and Tables
Schematic of the Mary Rose hull.
Degassing fountain at Lake Nyos, Cameroon.
Apoptosis in unirradiated bystander cells.
Secondary structure of S. aureus 6S RNA.
Fkbp52 expression in wild-type mouse uterus at day 5 of pregnancy.
