A new occurrence of the Early Jurassic brachiopod Anarhynchia from the Canadian Cordillera confirms its membership in chemosynthesis-based ecosystems

Cold seeps, where seepage of hydrocarbon-rich fluids occurs in the sea floor, are sites that harbor highly specialized ecosystems associated with distinctive carbonate sediments. Although their Mesozoic record is scarce and patchy, it commonly includes dimerelloid rhynchonellide brachiopods. Here we report a monospecific assemblage of Anarhynchia from a limestone boulder of early Pliensbachian (Early Jurassic) age in the Inklin Formation of the Whitehorse Trough in the Stikine terrane, from a locality at Atlin Lake in northern British Columbia. Specimens are among the largest known Mesozoic brachiopods, up to 9 cm in length, and described here as Anarhynchia smithi n. sp. Early precipitated carbonate cement phases of the limestone have carbon isotopic composition highly depleted in 13C, indicative of the influence of microbial oxidation of methane derived from a cold seep. Carbonate petrography of the banded-fibrous cement and other characteristic components supports this paleoenvironmental inference. Volcanogenic detrital grains in the matrix are indistinguishable from those in the sandstone layers in the siliciclastic sequence, suggesting that the seep carbonate is broadly coeval with the enclosing conglomerate. The new record extends the geographic range and species-level diversity of the genus, but supports its endemism to the East Pacific and membership in chemosynthesis-based ecosystems. The distribution of three distinct but congeneric species suggests that allopatric speciation occurred at separate sites along the active margin of western North America and Anarhynchia was restricted to seep and vent habitats in the Early Jurassic.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Improved protocols for functional analysis in the pathogenic fungus Aspergillus flavus

<p>Abstract</p> <p>Background</p> <p>An available whole genome sequence for <it>Aspergillus flavus </it>provides the opportunity to characterize factors involved in pathogenicity and to elucidate the regulatory networks involved in aflatoxin biosynthesis. Functional analysis of genes within the genome is greatly facilitated by the ability to disrupt or mis-express target genes and then evaluate their result on the phenotype of the fungus. Large-scale functional analysis requires an efficient genetic transformation system and the ability to readily select transformants with altered expression, and usually requires generation of double (or multi) gene deletion strains or the use of prototrophic strains. However, dominant selectable markers, an efficient transformation system and an efficient screening system for transformants in <it>A. flavus </it>are absent.</p> <p>Results</p> <p>The efficiency of the genetic transformation system for <it>A. flavus </it>based on uracil auxotrophy was improved. In addition, <it>A. flavus </it>was shown to be sensitive to the antibiotic, phleomycin. Transformation of <it>A. flavus </it>with the <it>ble </it>gene for resistance to phleomycin resulted in stable transformants when selected on 100 μg/ml phleomycin. We also compared the phleomycin system with one based on complementation for uracil auxotrophy which was confirmed by uracil and 5-fluoroorotic acid selection and via transformation with the <it>pyr4 </it>gene from <it>Neurospora crassa </it>and <it>pyrG </it>gene from <it>A. nidulans </it>in <it>A. flavus </it>NRRL 3357. A transformation protocol using <it>pyr4 </it>as a selectable marker resulted in site specific disruption of a target gene. A rapid and convenient colony PCR method for screening genetically altered transformants was also developed in this study.</p> <p>Conclusion</p> <p>We employed phleomycin resistance as a new positive selectable marker for genetic transformation of <it>A. flavus</it>. The experiments outlined herein constitute the first report of the use of the antibiotic phleomycin for transformation of <it>A. flavus</it>. Further, we demonstrated that this transformation protocol could be used for directed gene disruption in <it>A. flavus</it>. The significance of this is twofold. First, it allows strains to be transformed without having to generate an auxotrophic mutation, which is time consuming and may result in undesirable mutations. Second, this protocol allows for double gene knockouts when used in conjunction with existing strains with auxotrophic mutations.</p> <p>To further facilitate functional analysis in this strain we developed a colony PCR-based method that is a rapid and convenient method for screening genetically altered transformants. This work will be of interest to those working on molecular biology of aflatoxin metabolism in <it>A. flavus</it>, especially for functional analysis using gene deletion and gene expression.</p

Quasinormal Modes of AdS Black Holes and the Approach to Thermal Equilibrium

We investigate the decay of a scalar field outside a Schwarzschild anti de Sitter black hole. This is determined by computing the complex frequencies associated with quasinormal modes. There are qualitative differences from the asymptotically flat case, even in the limit of small black holes. In particular, for a given angular dependence, the decay is always exponential - there are no power law tails at late times. In terms of the AdS/CFT correspondence, a large black hole corresponds to an approximately thermal state in the field theory, and the decay of the scalar field corresponds to the decay of a perturbation of this state. Thus one obtains the timescale for the approach to thermal equilibrium. We compute these timescales for the strongly coupled field theories in three, four, and six dimensions which are dual to string theory in asymptotically AdS spacetimes.Comment: 25 pages, 9 figures extended discussion of horizon boundary conditions, added note on higher l mode

The Power of Brane-Induced Gravity

We study the role of the brane-induced graviton kinetic term in theories with large extra dimensions. In five dimensions we construct a model with a TeV-scale fundamental Planck mass and a {\it flat} extra dimension the size of which can be astronomically large. 4D gravity on the brane is mediated by a massless zero-mode, whereas the couplings of the heavy Kaluza-Klein modes to ordinary matter are suppressed. The model can manifest itself through the predicted deviations from Einstein theory in long distance precision measurements of the planetary orbits. The bulk states can be a rather exotic form of dark matter, which at sub-solar distances interact via strong 5D gravitational force. We show that the induced term changes dramatically the phenomenology of sub-millimeter extra dimensions. For instance, high-energy constraints from star cooling or cosmology can be substantially relaxed.Comment: 24 pages, 4 eps figures; v2 typos corrected; v3 1 ref. added; PRD versio

Hairy Black Holes in String Theory

Solutions of bosonic string theory are constructed which correspond to four-dimensional black holes with axionic quantum hair. The basic building blocks are the renormalization group flows of the CP1 model with a theta term and the SU(1,1)/U(1) WZW coset conformal field theory. However the solutions are also found to have negative energy excitations, and are accordingly expected to decay to the vacuum.Comment: 14 pages (References added