Extreme accumulation of nucleotides in simulated hydrothermal pore systems

We simulate molecular transport in elongated hydrothermal pore systems influenced by a thermal gradient. We find extreme accumulation of molecules in a wide variety of plugged pores. The mechanism is able to provide highly concentrated single nucleotides, suitable for operations of an RNA world at the origin of life. It is driven solely by the thermal gradient across a pore. On the one hand, the fluid is shuttled by thermal convection along the pore, whereas on the other hand, the molecules drift across the pore, driven by thermodiffusion. As a result, millimeter-sized pores accumulate even single nucleotides more than 108-fold into micrometer-sized regions. The enhanced concentration of molecules is found in the bulk water near the closed bottom end of the pore. Because the accumulation depends exponentially on the pore length and temperature difference, it is considerably robust with respect to changes in the cleft geometry and the molecular dimensions. Whereas thin pores can concentrate only long polynucleotides, thicker pores accumulate short and long polynucleotides equally well and allow various molecular compositions. This setting also provides a temperature oscillation, shown previously to exponentially replicate DNA in the protein-assisted PCR. Our results indicate that, for life to evolve, complicated active membrane transport is not required for the initial steps. We find that interlinked mineral pores in a thermal gradient provide a compelling high-concentration starting point for the molecular evolution of life

Brief Note: Characterization of Hydrophobic Stream Bacteria Based on Adhesion to n-Octane

Author Institution: Department of Biological Sciences, Kent State UniversityThe purpose of this study was to characterize stream bacterial communities based on cell surface hydrophobicity. Because hydrophobicity is related to adhesion we hypothesized that more hydrophobic bacteria would be found on solid surfaces than in water. Water, rock, and sediment from two northeastern Ohio streams were sampled and bacteria were plated on modified nutrient agar. Hydrophobicity was determined by measuring adherence to n-octane. No difference was found in the proportion of hydrophobic bacteria among habitats. Two hydrophobic isolates were identified as Sphingomonas paucimobilis and Chryseomonas luteola. A large proportion of hydrophobic bacteria were gram positive and urease positive; none were gelatinase positive. More hydrophobic than hydrophilic bacteria were able to grow using manatose or malatose as the only carbon source. These physiological differences indicate that hydrophobic bacteria may be able to utilize resources not available to hydrophilic bacteria

Abundance of Planktonic Virus-Like Particles in Lake Erie Subsurface Waters

Author Institution: Department of Biological Sciences, Kent State University - Trumbull Campus ; Department of Biological Sciences and Water Resources Research Institute, Kent State UniversityAbundance of virus-like particles (VLP) was determined in Lake Erie subsurface water. The relationship between VLP and the bacterial and phytoplankton communities were investigated. Viral and bacterial numbers were determined using nucleic acid stains and epifluorescent microscopy. Phytoplankton abundance was estimated by chlorophylls extraction. Viral abundance averaged 1.05 x 106 VLP/ml and the ratio of viral to bacterial number was less than 1.0 across most sampling sites and dates. Viral abundance was not correlated with either bacterial abundance or chlorophyll a concentration. Viral abundance was found to be most similar to other Great Lakes and marine systems and dissimilar to other freshwater systems

Dust Temperatures in the Infrared Space Observatory Atlas of Bright Spiral Galaxies

We examine far-infrared and submillimeter spectral energy distributions for galaxies in the Infrared Space Observatory Atlas of Bright Spiral Galaxies. For the 71 galaxies where we had complete 60-180 micron data, we fit blackbodies with lambda^-1 emissivities and average temperatures of 31 K or lambda^-2 emissivities and average temperatures of 22 K. Except for high temperatures determined in some early-type galaxies, the temperatures show no dependence on any galaxy characteristic. For the 60-850 micron range in eight galaxies, we fit blackbodies with lambda^-1, lambda-2, and lambda^-beta (with beta variable) emissivities to the data. The best results were with the lambda^-beta emissivities, where the temperatures were ~30 K and the emissivity coefficient beta ranged from 0.9 to 1.9. These results produced gas to dust ratios that ranged from 150 to 580, which were consistent with the ratio for the Milky Way and which exhibited relatively little dispersion compared to fits with fixed emissivities.Comment: AJ, 2003, in pres

Stomatin-like Protein 2 Links Mitochondria to T-Cell Receptor Signalosomes at the Immunological Synapse and Enhances T-Cell Activation

T cell activation through the antigen receptor (TCR) requires sustained signalling from microclusters in the peripheral region of the immunological synapse (IS). The bioenergetics of such prolonged signaling have been linked to the redistribution of mitochondria to the IS. Here, we report that stomatin-like protein-2 (SLP-2) plays an important role in this process by bridging polarized mitochondria to these signaling TCR microclusters or signalosomes in the IS in a polymerized actin-dependent manner. In this way, SLP-2 helps to sustain TCR-dependent signalling and enhances T cell activation

The Spectral Energy Distribution of Self-gravitating Interstellar Clouds I. Spheres

We derive the spectral energy distribution (SED) of dusty, isothermal, self gravitating, stable and spherical clouds externally heated by the ambient interstellar radiation field. For a given radiation field and dust properties, the radiative transfer problem is determined by the pressure of the surrounding medium and the cloud mass expressed as a fraction of the maximum stable cloud mass above which the clouds become gravitational unstable. To solve the radiative transfer problem a ray-tracing code is used to accurately derive the light distribution inside the cloud. This code considers both non isotropic scattering on dust grains and multiple scattering events. The dust properties inside the clouds are assumed to be the same as in the diffuse interstellar medium in our galaxy. We analyse the effect of the pressure, the critical mass fraction, and the ISRF on the SED and present brightness profiles in the visible, the IR/FIR and the submm/mm regime with the focus on the scattered emission and the thermal emission from PAH-molecules and dust grains.Comment: accepted for publication in ApJS, May 2008, v176n1 issu

A Global eDNA Comparison of Freshwater Bacterioplankton Assemblages Focusing on Large-River Floodplain Lakes of Brazil

With its network of lotic and lentic habitats that shift during changes in seasonal connection, the tropical and subtropical large-river systems represent possibly the most dynamic of all aquatic environments. Pelagic water samples were collected from Brazilian floodplain lakes (total n = 58) in four floodpulsed systems (Amazon [n = 21], Araguaia [n = 14], Paraná [n = 15], and Pantanal [n = 8]) in 2011–2012 and sequenced via 454 for bacterial environmental DNA using 16S amplicons; additional abiotic field and laboratory measurements were collected for the assayed lakes.We report here a global comparison of the bacterioplankton makeup of freshwater systems, focusing on a comparison of Brazilian lakes with similar freshwater systems across the globe. The results indicate a surprising similarity at higher taxonomic levels of the bacterioplankton in Brazilian freshwater with global sites. However, substantial novel diversity at the family level was also observed for the Brazilian freshwater systems. Brazilian freshwater bacterioplankton richness was relatively average globally. Ordination results indicate that Brazilian bacterioplankton composition is unique from other areas of the globe. Using Brazil-only ordinations, floodplain system differentiation most strongly correlated with dissolved oxygen, pH, and phosphate. Our data on Brazilian freshwater systems in combination with analysis of a collection of freshwater environmental samples from across the globe offers the first regional picture of bacterioplankton diversity in these important freshwater systems