102 research outputs found
Genome sequence of Salarchaeum sp. Strain JOR-1, an extremely halophilic archaeon from the Dead Sea
An extremely halophilic archaeon, Salarchaeum sp. strain JOR-1, was isolated from the east coast of the Dead Sea, Kingdom of Jordan, and sequenced using single-molecule real-time (SMRT) sequencing. The GC-rich 2.5-Mbp genome was composed of a circular chromosome and a megaplasmid. The genome contained 2,633 genes and was incorporated into HaloWeb.Fil: Anton, Brian P.. New England Biolabs; Estados UnidosFil: DasSarma, Priya. University of Maryland; Estados UnidosFil: MartÃnez, Fabiana Lilian. University of Maryland; Estados Unidos. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Universidad Nacional de Salta. Facultad de IngenierÃa. Instituto Nacional de Investigaciones para las Industrias QuÃmicas; ArgentinaFil: DasSarma, Satyajit L.. University of Maryland; Estados UnidosFil: Madadha, Mohammad Al. University of Jordan; Jordania. University of Maryland; Estados UnidosFil: Roberts, Richard J.. New England Biolabs; Estados UnidosFil: DasSarma, Shiladitya. University of Maryland; Estados Unido
Genome Sequences and Methylation Patterns of Natrinema versiforme BOL5-4 and Natrinema pallidum BOL6-1, Two Extremely Halophilic Archaea from a Bolivian Salt Mine
Two extremely halophilic archaea, namely, Natrinema versiforme BOL5-4 and Natrinema pallidum BOL6-1, were isolated from a Bolivian salt mine and their genomes sequenced using single-molecule real-time sequencing. The GC-rich genomes of BOL5-4 and BOL6-1 were 4.6 and 3.8 Mbp, respectively, with large chromosomes and multiple megaplasmids. Genome annotation was incorporated into HaloWeb and methylation patterns incorporated into REBASE.Fil: DasSarma, Priya. University of Maryland; Estados UnidosFil: Anton, Brian P.. New England BioLabs; Estados UnidosFil: DasSarma, Satyajit L.. University of Maryland; Estados UnidosFil: MartÃnez, Fabiana Lilian. University of Maryland; Estados Unidos. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria QuÃmica. Universidad Nacional de Salta. Facultad de IngenierÃa. Instituto de Investigaciones para la Industria QuÃmica; ArgentinaFil: Guzman, Daniel. Universidad Mayor de San Simón; BoliviaFil: Roberts, Richard J.. New England BioLabs; Estados UnidosFil: DasSarma, Shiladitya. University of Maryland; Estados Unido
Complete Genome Sequence and Methylome Analysis of Micrococcus luteus SA211, a Halophilic, Lithium-Tolerant Actinobacterium from Argentina
Micrococcus luteus has been found in a wide range of habitats. We report the complete genome sequence and methylome analysis of strain SA211 isolated from a hypersaline, lithium-rich, high-altitude salt flat in Argentina with single-molecule real-time sequencing.Fil: MartÃnez, Fabiana Lilian. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria QuÃmica. Universidad Nacional de Salta. Facultad de IngenierÃa. Instituto de Investigaciones para la Industria QuÃmica; Argentina. University of Maryland; Estados UnidosFil: Anton, B. P.. New England Biolabs; Estados UnidosFil: DasSarma, P.. University of Maryland; Estados UnidosFil: Rajal, Verónica Beatriz. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria QuÃmica. Universidad Nacional de Salta. Facultad de IngenierÃa. Instituto de Investigaciones para la Industria QuÃmica; ArgentinaFil: Irazusta, Verónica Patricia. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria QuÃmica. Universidad Nacional de Salta. Facultad de IngenierÃa. Instituto de Investigaciones para la Industria QuÃmica; ArgentinaFil: Roberts, Roy. New England Biolabs; Estados UnidosFil: DasSarma, S.. University of Maryland; Estados Unido
Conductivity in quasi two-dimensional systems
The conductivity in quasi two-dimensional systems is calculated using the
quantum kinetic equation. Linearizing the Lenard-Balescu collision integral
with the extension to include external field dependences allows one to
calculate the conductivity with diagrams beyond the GW approximation including
maximally crossed lines. Consequently the weak localization correction as an
interference effect appears here from the field dependence of the collision
integral (the latter dependence sometimes called intra-collisional field
effect). It is shown that this weak localization correction has the same origin
as the Debye-Onsager relaxation effect in plasma physics. The approximation is
applied to a system of quasi two-dimensional electrons in hetero-junctions
which interact with charged and neutral impurities and the low temperature
correction to the conductivity is calculated analytically. It turns out that
the dynamical screening due to charged impurities leads to a linear temperature
dependence, while the scattering from neutral impurities leads to the usual
Fermi-liquid behavior. By considering an appropriate mass action law to
determine the ratio of charged to neutral impurities we can describe the
experimental metal-insulator transition at low temperatures as a Mott-Hubbard
transition.Comment: 7 pages 7 pages appendix 11 figure
Spin-isospin textured excitations in a double layer at filling factor
We study the charged excitations of a double layer at filling factor 2 in the
ferromagnetic regime. In a wide range of Zeeman and tunneling splittings we
find that the low energy charged excitations are spin-isospin textures with the
charge mostly located in one of the layers. As tunneling increases, the parent
spin texture in one layer becomes larger and it induces, in the other layer, a
shadow spin texture antiferromagnetically coupled to the parent texture. These
new quasiparticles should be observable by measuring the strong dependence of
its spin on tunneling and Zeeman couplings.Comment: 4 pages, 4 figure
Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment
Here we review how environmental context can be used to interpret whether O2
is a biosignature in extrasolar planetary observations. This paper builds on
the overview of current biosignature research discussed in Schwieterman et al.
(2017), and provides an in-depth, interdisciplinary example of biosignature
identification and observation that serves as a basis for the development of
the general framework for biosignature assessment described in Catling et al.,
(2017). O2 is a potentially strong biosignature that was originally thought to
be an unambiguous indicator for life at high-abundance. We describe the
coevolution of life with the early Earth's environment, and how the interplay
of sources and sinks in the planetary environment may have resulted in
suppression of O2 release into the atmosphere for several billion years, a
false negative for biologically generated O2. False positives may also be
possible, with recent research showing potential mechanisms in exoplanet
environments that may generate relatively high abundances of atmospheric O2
without a biosphere being present. These studies suggest that planetary
characteristics that may enhance false negatives should be considered when
selecting targets for biosignature searches. Similarly our ability to interpret
O2 observed in an exoplanetary atmosphere is also crucially dependent on
environmental context to rule out false positive mechanisms. We describe future
photometric, spectroscopic and time-dependent observations of O2 and the
planetary environment that could increase our confidence that any observed O2
is a biosignature, and help discriminate it from potential false positives. By
observing and understanding O2 in its planetary context we can increase our
confidence in the remote detection of life, and provide a model for
biosignature development for other proposed biosignatures.Comment: 55 pages. The paper is the second in a series of 5 review manuscripts
of the NExSS Exoplanet Biosignatures Workshop. Community commenting is
solicited at https://nexss.info/groups/ebww
Surface and Temporal Biosignatures
Recent discoveries of potentially habitable exoplanets have ignited the
prospect of spectroscopic investigations of exoplanet surfaces and atmospheres
for signs of life. This chapter provides an overview of potential surface and
temporal exoplanet biosignatures, reviewing Earth analogues and proposed
applications based on observations and models. The vegetation red-edge (VRE)
remains the most well-studied surface biosignature. Extensions of the VRE,
spectral "edges" produced in part by photosynthetic or nonphotosynthetic
pigments, may likewise present potential evidence of life. Polarization
signatures have the capacity to discriminate between biotic and abiotic "edge"
features in the face of false positives from band-gap generating material.
Temporal biosignatures -- modulations in measurable quantities such as gas
abundances (e.g., CO2), surface features, or emission of light (e.g.,
fluorescence, bioluminescence) that can be directly linked to the actions of a
biosphere -- are in general less well studied than surface or gaseous
biosignatures. However, remote observations of Earth's biosphere nonetheless
provide proofs of concept for these techniques and are reviewed here. Surface
and temporal biosignatures provide complementary information to gaseous
biosignatures, and while likely more challenging to observe, would contribute
information inaccessible from study of the time-averaged atmospheric
composition alone.Comment: 26 pages, 9 figures, review to appear in Handbook of Exoplanets.
Fixed figure conversion error
Diurnally Entrained Anticipatory Behavior in Archaea
By sensing changes in one or few environmental factors biological systems can anticipate future changes in multiple factors over a wide range of time scales (daily to seasonal). This anticipatory behavior is important to the fitness of diverse species, and in context of the diurnal cycle it is overall typical of eukaryotes and some photoautotrophic bacteria but is yet to be observed in archaea. Here, we report the first observation of light-dark (LD)-entrained diurnal oscillatory transcription in up to 12% of all genes of a halophilic archaeon Halobacterium salinarum NRC-1. Significantly, the diurnally entrained transcription was observed under constant darkness after removal of the LD stimulus (free-running rhythms). The memory of diurnal entrainment was also associated with the synchronization of oxic and anoxic physiologies to the LD cycle. Our results suggest that under nutrient limited conditions halophilic archaea take advantage of the causal influence of sunlight (via temperature) on O2 diffusivity in a closed hypersaline environment to streamline their physiology and operate oxically during nighttime and anoxically during daytime
The GAAS Metagenomic Tool and Its Estimations of Viral and Microbial Average Genome Size in Four Major Biomes
Metagenomic studies characterize both the composition and diversity of uncultured viral and microbial communities. BLAST-based comparisons have typically been used for such analyses; however, sampling biases, high percentages of unknown sequences, and the use of arbitrary thresholds to find significant similarities can decrease the accuracy and validity of estimates. Here, we present Genome relative Abundance and Average Size (GAAS), a complete software package that provides improved estimates of community composition and average genome length for metagenomes in both textual and graphical formats. GAAS implements a novel methodology to control for sampling bias via length normalization, to adjust for multiple BLAST similarities by similarity weighting, and to select significant similarities using relative alignment lengths. In benchmark tests, the GAAS method was robust to both high percentages of unknown sequences and to variations in metagenomic sequence read lengths. Re-analysis of the Sargasso Sea virome using GAAS indicated that standard methodologies for metagenomic analysis may dramatically underestimate the abundance and importance of organisms with small genomes in environmental systems. Using GAAS, we conducted a meta-analysis of microbial and viral average genome lengths in over 150 metagenomes from four biomes to determine whether genome lengths vary consistently between and within biomes, and between microbial and viral communities from the same environment. Significant differences between biomes and within aquatic sub-biomes (oceans, hypersaline systems, freshwater, and microbialites) suggested that average genome length is a fundamental property of environments driven by factors at the sub-biome level. The behavior of paired viral and microbial metagenomes from the same environment indicated that microbial and viral average genome sizes are independent of each other, but indicative of community responses to stressors and environmental conditions
- …