Deciphering the light signal transduction mechanism in Staphylococcus aureus

Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii have been recognized by the WHO and the CDC as critical human pathogens. These microorganisms belong to the ESKAPE group, so named since they are capable of "escaping" antibiotic treatments. The infections caused by these pathogens result in a dramatic increase in the costs of medical care. Previous results from our laboratory have shown that these microorganisms can sense and respond to light. In S. aureus, light has been shown to modulate important pathogenicity determinants such as alpha toxin-dependent hemolysis, as well as virulence in an epithelial infection model, which could have implications in human infections. Light also regulates persistence, metabolism, and the ability to kill competitors such as C. albicans, in this microorganism. To our knowledge, the ability of S. aureus to sense and respond to light constitutes a newly described physiological trait. These pathogens could sense light to synchronize their behavior with the circadian rhythm of their hosts, likely as a strategy to optimize infection development. Identification of the photoreceptors involved in light sensing in S. aureus would provide important insights into the light signal transduction cascade. Despite no traditional photoreceptors were found encoded in its genome, we identified the presence of three putative proteins containing GAF domains. GAF domains have been shown to be part of phytochromes and cyanobacteriochromes along with other domains such as PHY and PAS. While in two of them the GAF domain encompasses the full-length protein sequence, suggesting a new photoreceptor architecture, the last one harbors a GAF N-terminal domain associated with a C-terminal histidine kinase. The genomic environment of each putative photoreceptor was determined, and genes such as LuxR, involved in a quorum-sensing regulation; and DegU, identified as a response regulator of bacterial motility, virulence and biofilm formation, were found in their close proximity. Recent results from our group show that motility in S. aureus is not only modulated by blue light, but also by red and green lights. This is compatible with multiple GAF photoreceptors as they exist in two thermally stable states interconvertible by light, absorbing in different regions of the spectrum. Moreover, the presence of three cysteine residues were observed, residue shown to be essential for binding of the bilin chromophore. In this sense, it is interesting to note that S. aureus produces Staphylobilin as a product of heme metabolism. In addition, we amplified the DNA fragments encoding these putative photoreceptors from S. aureus USA300 strain, and subcloned them into the expression vector pET-TEV, to corroborate that they are active photoreceptors upon light absorption. Finally, proteomic results are discussed which suggest new pathways modulated by light in S. aureus such as cell wall synthesis and recycling.Fil: Arana, N. A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosintéticos y Bioquímicos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos; ArgentinaFil: Müller, G. L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosintéticos y Bioquímicos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos; ArgentinaFil: Mussi, María Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosintéticos y Bioquímicos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos; ArgentinaLVII SAIB Meeting; XVI SAMIGE MeetingArgentinaSociedad Argentina De Investigación Bioquímica Y Biología MolecularSociedad Argentina de Microbiología Genera

High-energy radiation from collisions of high-velocity clouds and the Galactic disc

High-velocity clouds (HVCs) are interstellar clouds of atomic hydrogen that do not follow normal Galactic rotation and have velocities of a several hundred kilometres per second. A considerable number of these clouds are falling down towards the Galactic disc. HVCs form large and massive complexes, so if they collide with the disc a great amount of energy would be released into the interstellar medium. The cloud-disc interaction produces two shocks: one propagates through the cloud and the other through the disc. The properties of these shocks depend mainly on the cloud velocity and the disc-cloud density ratio. In this work, we study the conditions necessary for these shocks to accelerate particles by diffusive shock acceleration and we study the non-thermal radiation that is produced. We analyse particle acceleration in both the cloud and disc shocks. Solving a time-dependent two-dimensional transport equation for both relativistic electrons and protons, we obtain particle distributions and non-thermal spectral energy distributions. In a shocked cloud, significant synchrotron radio emission is produced along with soft gamma rays. In the case of acceleration in the shocked disc, the non-thermal radiation is stronger; the gamma rays, of leptonic origin, might be detectable with current instruments. A large number of protons are injected into the Galactic interstellar medium, and locally exceed the cosmic ray background. We conclude that under adequate conditions the contribution from HVC-disc collisions to the galactic population of relativistic particles and the associated extended non-thermal radiation might be important.Facultad de Ciencias Astronómicas y Geofísica

Detailed study of the direct numerical observation of the Kramers turnover in the LiNC⇌LiCN isomerization rate

The following article appeared in Journal of Chemical Physics 137.20 (2012): 204301 and may be found at http://scitation.aip.org/content/aip/journal/jcp/137/20/10.1063/1.4766257According to Kramers, rates of molecular process are expected to follow a rise and fall from low friction (at little to no interaction with the environment) to high friction (at typical liquid densities and above). This so-called Kramers turnover was recently observed and delineated in the case of the LiNC⇌LiCN isomerization reaction in the presence of an argon bath [P. García-Müller, R. Hernandez, R. M. Benito, and F. Borondo, Phys. Rev. Lett. 101, 178302 (2008)]. The rates were obtained using direct molecular dynamics of an all-atom representation and the Langevin dynamics of a projected representation. We now provide further evidence that the forward and backward rates are indeed exhibiting the turnover. The rates are also seen to agree remarkably well with the Pollak-Grabert-Hänggi rate formulas in regimes satisfying the theory underlying assumptions. At higher temperatures, when the theory is expected to fail, the solvated LiCN isomerization continues to exhibit activated dynamics following the turnoverThis work has been supported by the Spanish MINECO under projects MTM2009-14621 and ICMAT Severo Ochoa SEV-2011-0087. It also has been partially supported by the U.S. National Science Foundation under Grant No. CHE-1112067. Travel between partners was partially supported through the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/ under REA Grant Agreement No. 29497

Expression profile of transcripts encoding cell wall remodelling proteins in tomato fruit cv. Micro-Tom subjected to 15°C storage

To extend fruit market life, tomatoes are harvested before red ripe and kept at temperatures below optimum (20°C). In this work, Micro-Tom tomatoes stored at 20°C (normal ripening) were compared with those stored at 15°C or 4°C (chilling injury inducer) for 7 days. In contrast to 4°C, storage at 15°C delayed ripening with the benefit of not enhancing oxidative metabolism and of enabling ripening upon being transferred to 20°C. The transcriptional expression profile of enzymes related to cell wall metabolism was compared at the three temperatures. Although endo-β-1,4-glucanase (Cel1), which is associated with fruit decay, was largely increased after removal from 4°C storage, its expression was not modified in fruits stored at 15°C. Enhanced transcriptional expression of xyloglucan endotransgylcosylase/hydrolases (XTHs) XTH1, –2, –10 and –11, and of two β-xylosidases (Xyl1–2) was detected in fruits stored at 15°C with respect to those at 20°C. Following 2 days at 20°C, these transcripts remained higher in fruits stored at 15°C and XHT3 and –9 also increased. Ethylene evolution was similar in fruits kept at 15°C and 20°C; thus, the changes in the transcript profile and fruit properties between these treatments may be under the control of factors other than ethylene.EEA San PedroFil: Müller, Gabriela L. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI); Argentina.Fil: Budde, Claudio Olaf. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; Argentina.Fil: Lauxmann, Martin A. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI); Argentina.Fil: Triassi, Agustina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI); Argentina.Fil: Andreo, Carlos Santiago. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI); Argentina.Fil: Drincovich, María Fabiana. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI); Argentina.Fil: Lara, María Valeria. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI); Argentina

Polyethylene Oxide/Sodium Sulfonamide Polymethacrylate Blends as Highly Conducting Single-Ion Solid Polymer Electrolytes

In this work, blends of polyethylene oxide (PEO) and poly(sodium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethanesulfonyl) imide) (PNaMTFSI) in different compositions were investigated for their application as solid electrolytes for sodium batteries. PNaMTFSI and PEO are miscible, exhibiting only one Tg in the whole range of compositions. PNaMTFSI was shown to reduce the crystal growth rate of PEO crystals but increase PEO nucleation, making the overall crystallization rate higher in blends with 15 and 30 wt % PNaMTFSI. The ionic conductivity is also affected by the blend composition. The highest values of ionic conductivity were observed with 15 and 30 wt % PNaMTFSI at high temperatures equal to 5.84 × 10–5 and 7.74 × 10–5 S cm–1 at 85 °C, respectively, with values of sodium-ion transference numbers of higher than 0.83 and electrochemical stability between 3.5 and 4.5 V versus Na+/Na0 depending on the composition, which opens the possibility of its use in sodium batteries. Finally, a comparison was made between the effect of sodium and lithium on these types of electrolytes, showing that sodium electrolytes have a lower ionic conductivity due to the larger size of the Na cation. The differences in the spherulitic growth rate and overall crystallization rate between Li and Na-containing electrolytes were compared and rationalized in terms of the blends’ intermolecular interactions and the relative contribution of primary nucleation and growth.We acknowledge the funding by Agencia Estatal de Investigación (no. PLEC2021-007929). This work has received funding from the Basque Government through grant no. IT1503-22

Origin, distribution, and potential risk factors associated with influenza A virus in swine in two production systems in Guatemala

Background: Guatemala is the country with the largest swine production in Central America; however, evidence of influenza A virus (IAV) in pigs has not been clearly delineated. Objectives: In this study, we analyzed the presence and spatial distribution of IAV in commercial and backyard swine populations. Methods: Samples from two nationwide surveys conducted in 2010 and 2011 were tested using virological (rRT-PCR and virus isolation) and serological (ELISA and hemagglutination inhibition) assays to detect IAV. Results: Influenza A virus was detected in 15.7% of the sampled pigs (30.6% of herds) in 2010 and in 11.7% (24.2% of herds) in 2011. The percentage of seropositive pigs was 10.6% (16.1% of herds) and 1.4% (3.1% of herds) for each year, respectively. Three pandemic H1N1 and one seasonal human-like H3N2 viruses were isolated. Antibodies against viruses from different genetic clusters were detected. No reassortant strains with swine viruses were detected. The H3N2 virus was closely related to human viruses that circulated in Central America in 2010, distinct to the most recent human seasonal vaccine lineages. Spatial clusters of rRT-PCR positive herds were detected each year by scan statistics. Conclusions: Our results demonstrate circulation of IAV throughout Guatemala and identify commercial farms, animal health status, and age as potential risk factors associated with IAV infection and exposure. Detection of human-origin viruses in pigs suggests a role for humans in the molecular epidemiology of IAV in swine in Guatemala and evidences gaps in local animal and human surveillance

Supernucleation Dominates Lignin/Poly(ethylene oxide) Crystallization Kinetics

The effect of lignin nanoparticles (LNPs) on the crystallization kinetics of poly(ethylene oxide) (PEO) is examined. Lignin from spruce and ionic isolation was used to prepare LNPs with a number-averaged diameter of 85 nm (with a relatively large polydispersity) by an ultrasonication method. PEO-based nanocomposites with four different LNP contents (5, 10, 15, and 20 wt %) were prepared and subject to isothermal and nonisothermal crystallization protocols in a series of experiments. Scanning electron microscopy (SEM) images showed well-dispersed LNPs in the crystallized PEO matrix. The incorporation of LNPs exponentially increases nucleation density at moderate loadings, with this trend apparently saturating at higher loadings. However, the spherulitic growth rate decreases monotonically with LNP loading. This is attributed to the substantial PEO/LNP affinity, which impacts chain diffusion and induces supernucleation effect (with efficiencies in the order of 200%), but leads to slower growth rates. The overall crystallization kinetics, measured by the DSC, shows faster nanocomposite crystallization rates relative to the neat PEO at all LNP contents examined. This indicates that the supernucleation effect of LNPs dominates over the decrease in the growth rates, although its influence slightly decreases as the LNP content increases. The strong hydrogen-bonded interactions between the LNPs and the PEO are thus reminiscent of confinement effects found in polymer-grafted NP nanocomposites (e.g., PEO-g-SiO2/PEO) in the brush-controlled regime.This work received funding from the Basque Government through grant IT1503 - 22. S.K.K . acknowledges funding by the U.S. Department of Energy, Office of Science, grants DE- SC0018182, DE-SC0018135, and DE-SC0018111. The authors acknowledged the financial support of Fundacion Losano, PIP2011 848, and PUE No. 22920160100007 (CONICET) . The authors acknowledge the support of Ana Martínez Amesti, Microscopy: Polymer Characterization Research Service, SGIker (UPV/EHU)

On numerical relativistic hydrodynamics and barotropic equations of state

The characteristic formulation of the relativistic hydrodynamic equations (Donat et al 1998 J. Comput. Phys. 146 58), which has been implemented in many relativistic hydro-codes that make use of Godunov-type methods, has to be slightly modified in the case of evolving barotropic flows. For a barotropic equation of state, a removable singularity appears in one of the eigenvectors. The singularity can be avoided by means of a simple renormalization which makes the system of eigenvectors well defined and complete. An alternative strategy for the particular case of barotropic flows is discussed.Comment: 7 pages, no figures. Accepted for publication in Class. Quantum Gra

Coronal voids and their magnetic nature

Context. Extreme ultraviolet (EUV) observations of the quiet solar atmosphere reveal extended regions of weak emission compared to the ambient quiescent corona. The magnetic nature of these coronal features is not well understood.Aims. We study the magnetic properties of the weakly emitting extended regions, which we name coronal voids. In particular, we aim to understand whether these voids result from a reduced heat input into the corona or if they are associated with mainly unipolar and possibly open magnetic fields, similar to coronal holes. Methods. We defined the coronal voids via an intensity threshold of 75% of the mean quiet-Sun (QS) EUV intensity observed by the high- resolution EUV channel (HRIEUV) of the Extreme Ultraviolet Imager on Solar Orbiter. The line-of-sight magnetograms of the same solar region recorded by the High Resolution Telescope of the Polarimetric and Helioseismic Imager allowed us to compare the photospheric magnetic field beneath the coronal voids with that in other parts of the QS.Results. The coronal voids studied here range in size from a few granules to a few supergranules and on average exhibit a reduced intensity of 67% of the mean value of the entire field of view. The magnetic flux density in the photosphere below the voids is 76% (or more) lower than in the surrounding QS. Specifically, the coronal voids show much weaker or no network structures. The detected flux imbalances fall in the range of imbalances found in QS areas of the same size. Conclusions. We conclude that coronal voids form because of locally reduced heating of the corona due to reduced magnetic flux density in the photosphere. This makes them a distinct class of (dark) structure, different from coronal holes