dUTPase based switch controls transfer of virulence genes in order to preserve integrity of the transferred mobile genetic elements

dUTPases ubiquitously regulate cellular dUTP levels to preserve genome integrity. Recently, several other cellular processes were reported to be controlled by dUTPases including the horizontal transfer of Staphylococcus aureus pathogenicity islands (SaPI). SaPIs are mobil genetic elements that encode virulence enhancing factors e.g. toxins. Here, phage dUTPases were proposed to counteract the repressor protein (Stl) and promote SaPI excision and transfer. A G protein-like mechanism was proposed which is unexpected in light of the kinetic mechanism of dUTPase. Here we investigate the molecular mechanism of SaPI transfer regulation, using numerous dUTPase variants and a wide range of in vitro methods (steady-state and transient kinetics, VIS and fluorescence spectroscopy, EMSA, quartz crystal microbalance, X-ray crystallography). Our results unambiguously show that Stl inhibits the enzymatic activity of dUTPase in the nM concentration range and dUTP strongly inhibits the dUTPase: Stl complexation. These results identify Stl as a highly potent dUTPase inhibitor protein and disprove the G protein-like mechanism. Importantly, our results clearly show that the dUTPase:dUTP complex is inaccessible to the Stl repressor. Unlike in small GTPases, hydrolysis of the substrate nucleoside triphosphate (dUTP in this case) is required prior to the interaction with the partner (Stl repressor in this case). We propose that dUTPase can efficiently interact with Stl and induce SaPI excision only if the cellular dUTP level is low (i.e. when dUTPase resides mainly in the apo enzyme form) while high dUTP levels would inhibit SaPI transfer. This mechanism may serve the preservation of the integrity of the transferred SaPI genes and links the well-known metabolic role of dUTPases to their newly revealed regulatory function in spread of virulence factors

Evolution of monogenetic rhyolite volcanoes: Vinicky, Eastern Slovakia

Four essential volcanic units have been recognized in the late Middle Miocene rhyolite complex at the southern side of the Zemplín horst next to the village Viničky. A succession of ash/pumice flow, surge and fall deposits separated by horizons of eolian dust and paleosoil in total thickness >15 m forms the lower unit. It represents distal facies deposits of subplinian/plinian/phreatoplinian type eruptions at unidentified centers. The second unit rests upon the lower one with unconformity marking a period of erosion. It consists of coarse phreatic/phreatomagmatic pyroclastic rocks with fragments of basement rocks and glassy dacite/ rhyodacite. They represent proximal facies of a phreatomagmatic pyroclastic ring. Both units are truncated by a rhyolite extrusive dome, formed of perlite and perlitic breccias at its margin. Emplacement of the dome concluded activity of local centers northwest of Viničky. An extensive rhyolite coulee represents the fourth, uppermost volcanic unit. It is 40 – 70 m thick, formed of felsitic rhyolite with perlite and perlitic breccia at the base. Orientation of flow banding implies that the Borsuk extrusive dome 1 km northeast of Viničky was a source of the coulee. The dome and coulee form together one rhyolite body of the dome-flow type. With exception of the distal facies tuffs at the base the rhyolite complex represents most probably products of three overlapping monogenetic volcanoe

Ground state of a partially melted Wigner molecule

We consider three spinless fermions free to move on 2d square lattice with periodic boundary conditions and interacting via a U/r Coulomb repulsion. When the Coulomb energy to kinetic energy ratio r_s is large, a rigid Wigner molecule is formed. As r_s decreases, we show that melting proceeds via an intermediate regime where a floppy two particle molecule coexists with a partially delocalized particle. A simple ansatz is given to describe the ground state of this mesoscopic solid-liquid regime.Comment: to appear in Europhysics Letter

Quantification of an atmospheric nucleation and growth process as a single source of aerosol particles in a city

Effects of a new aerosol particle formation (NPF) and particle diameter growth process as a single source of atmospheric particle number concentrations were evaluated and quantified on the basis of experimental data sets obtained from particle number size distribution measurements in the city centre and near-city background of Budapest for 5 years. Nucleation strength factors for a nucleation day (NSFNUC) and for a general day (NSFGEN) were derived separately for seasons and full years. The former characteristic represents the concentration increment of ultrafine (UF) particles specifically on nucleation days with respect to accumulation-mode (regional background) concentrations (particles with equivalent diameters of 100–1000 nm; N100−1000) due solely to the nucleation process. The latter factor expresses the contribution of nucleation to particle numbers on general days; thus, it represents a longer time interval such as season or year. The nucleation source had the largest effect on the concentrations around noon and early afternoon, as expected. During this time interval, it became the major source of particles in the near-city background. Nucleation increased the daily mean concentrations on nucleation days by mean factors of 2.3 and 1.58 in the near-city background and city centre, respectively. Its effect was largest in winter, which was explained by the substantially lower N100−1000 levels on nucleation days than those on non-nucleation days. On an annual timescale, 37 % of the UF particles were generated by nucleation in the near-city background, while NPF produced 13 % of UF particles in the city centre. The differences among the annual mean values, and among the corresponding seasonal mean values, were likely caused by the variability in controlling factors from year to year. The values obtained represent the lower limits of the contributions. The shares determined imply that NPF is a non-negligible or substantial source of particles in near-city background environments and even in city centres, where the vehicular road emissions usually prevail. Atmospheric residence time of nucleation-mode particles was assessed by a decay curve analysis, and a mean of 02:30 was obtained. The present study suggests that the health-related consequences of the atmospheric NPF and growth process in cities should also be considered in addition to its urban climate implications