A small molecule that disrupts S. Typhimurium membrane voltage without cell lysis reduces bacterial colonization of mice

As pathogenic bacteria become increasingly resistant to antibiotics, antimicrobials with mechanisms of action distinct from current clinical antibiotics are needed. Gram-negative bacteria pose a particular problem because they defend themselves against chemicals with a minimally permeable outer membrane and with efflux pumps. During infection, innate immune defense molecules increase bacterial vulnerability to chemicals by permeabilizing the outer membrane and occupying efflux pumps. Therefore, screens for compounds that reduce bacterial colonization of mammalian cells have the potential to reveal unexplored therapeutic avenues. Here we describe a new small molecule, D66, that prevents the survival of a human Gram-negative pathogen in macrophages. D66 inhibits bacterial growth under conditions wherein the bacterial outer membrane or efflux pumps are compromised, but not in standard microbiological media. The compound disrupts voltage across the bacterial inner membrane at concentrations that do not permeabilize the inner membrane or lyse cells. Selection for bacterial clones resistant to D66 activity suggested that outer membrane integrity and efflux are the two major bacterial defense mechanisms against this compound. Treatment of mammalian cells with D66 does not permeabilize the mammalian cell membrane but does cause stress, as revealed by hyperpolarization of mitochondrial membranes. Nevertheless, the compound is tolerated in mice and reduces bacterial tissue load. These data suggest that the inner membrane could be a viable target for anti-Gram-negative antimicrobials, and that disruption of bacterial membrane voltage without lysis is sufficient to enable clearance from the host.     

Discharge�Ccalcium concentration relationships in streams of the Amazon and Cerrado of Brazil: soil or land use controlled

Stream discharge?Cconcentration relationships are indicators of terrestrial ecosystem function. Throughout the Amazon and Cerrado regions of Brazil rapid changes in land use and land cover may be altering these hydrochemical relationships. The current analysis focuses on factors controlling the discharge?Ccalcium (Ca) concentration relationship since previous research in these regions has demonstrated both positive and negative slopes in linear log₁₀discharge?Clog₁₀Ca concentration regressions. The objective of the current study was to evaluate factors controlling stream discharge?CCa concentration relationships including year, season, stream order, vegetation cover, land use, and soil classification. It was hypothesized that land use and soil class are the most critical attributes controlling discharge?CCa concentration relationships. A multilevel, linear regression approach was utilized with data from 28 streams throughout Brazil. These streams come from three distinct regions and varied broadly in watershed size (<1 to >10⁶ ha) and discharge (10^?5.7?C10^3.2 m³ s^?1). Linear regressions of log₁₀Ca versus log₁₀discharge in 13 streams have a preponderance of negative slopes with only two streams having significant positive slopes. An ANOVA decomposition suggests the effect of discharge on Ca concentration is large but variable. Vegetation cover, which incorporates aspects of land use, explains the largest proportion of the variance in the effect of discharge on Ca followed by season and year. In contrast, stream order, land use, and soil class explain most of the variation in stream Ca concentration. In the current data set, soil class, which is related to lithology, has an important effect on Ca concentration but land use, likely through its effect on runoff concentration and hydrology, has a greater effect on discharge?Cconcentration relationships.     

YphC and YsxC GTPases assist the maturation of the central protuberance,GTPase associated region and functional core of the 50S ribosomal subunit

YphC and YsxC are GTPases in Bacillus subtilis that facilitate the assembly of the 50S ribosomal subunit, however their roles in this process are still uncharacterized. To explore their function, we used strains in which the only copy of the yphC or ysxC genes were under the control of an inducible promoter. Under depletion conditions, they accumulated incomplete ribosomal subunits that we named 45S_YphC and 44.5S_YsxC particles. Quantitative mass spectrometry analysis and the 5–6 Å resolution cryo-EM maps of the 45S_YphC and 44.5S_YsxC particles revealed that the two GTPases participate in the maturation of the central protuberance, GTPase associated region and key RNA helices in the A, P and E functional sites of the 50S subunit. We observed that YphC and YsxC bind specifically to the two immature particles, suggesting that they represent either on-pathway intermediates or that their structure has not significantly diverged from that of the actual substrate. These results describe the nature of these immature particles, a widely used tool to study the assembly process of the ribosome. They also provide the first insights into the function of YphC and YsxC in 50S subunit assembly and are consistent with this process occurring through multiple parallel pathways, as it has been described for the 30S subunit.     

Digoxin Suppresses Pyruvate Kinase M2-Promoted HIF-1α Transactivation in Steatohepatitis

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Rapid up-regulation of alpha4 integrin-mediated leukocyte adhesion by transforming growth factor-beta1

The alpha4 integrins (alpha4beta1 and alpha4beta7) are cell surface heterodimers expressed mostly on leukocytes that mediate cell-cell and cell-extracellular matrix adhesion. A characteristic feature of alpha4 integrins is that their adhesive activity can be subjected to rapid modulation during the process of cell migration. Herein, we show that transforming growth factor-beta1 (TGF-beta1) rapidly (0.5-5 min) and transiently up-regulated alpha4 integrin-dependent adhesion of different human leukocyte cell lines and human peripheral blood lymphocytes (PBLs) to their ligands vascular cell adhesion molecule-1 (VCAM-1) and connecting segment-1/fibronectin. In addition, TGF-beta1 enhanced the alpha4 integrin-mediated adhesion of PBLs to tumor necrosis factor-alpha-treated human umbilical vein endothelial cells, indicating the stimulation of alpha4beta1/VCAM-1 interaction. Although TGF-beta1 rapidly activated the small GTPase RhoA and the p38 mitogen-activated protein kinase, enhanced adhesion did not require activation of both signaling molecules. Instead, polymerization of actin cytoskeleton triggered by TGF-beta1 was necessary for alpha4 integrin-dependent up-regulated adhesion, and elevation of intracellular cAMP opposed this up-regulation. Moreover, TGF-beta1 further increased cell adhesion mediated by alpha4 integrins in response to the chemokine stromal cell-derived factor-1alpha. These data suggest that TGF-beta1 can potentially contribute to cell migration by dynamically regulating cell adhesion mediated by alpha4 integrins.     

Six new non-native ants (Formicidae) in the Canary Islands and their possible impacts

Biological invasions are one of the main causes of biodiversity loss, especially on oceanic islands. Ants are among the most damaging pests in the world. After systematic sampling of more than 1,000 localities in the Canary Islands, six new exotic ant species are reported for the first time: Pheidole bilimeki (Myrmicinae), Pheidole navigans (Myrmicinae), Strumigenys membranifera (Myrmicinae), Brachymyrmex cordemoyi (Formicinae), Tapinoma darioi (Dolichoderinae) and Technomyrmex pallipes (Dolichoderinae). Moreover, another two recently reported species have been genetically confirmed. Morphological and genetic data were analysed to confirm the identity of the new records. For each species, information regarding identification, distribution, global invasive records and possible impacts is given. The arrival of these species may endanger local biodiversity.     

Structural determinants stabilizing the axial channel of ClpP for substrate translocation

Acyldepsipeptides (ADEPs) antibiotics bind to Escherichia coli ClpP mimicking the interactions that the IGL/F loops in ClpA or ClpX ATPases establish with the hydrophobic pockets surrounding the axial pore of the tetradecamer that the protease forms. ADEP binding induces opening of the gates blocking the axial channel of ClpP and allowing protein substrates to be translocated and hydrolysed in the degradation chamber. To identify the structural determinants stabilizing the open conformation of the axial channel for efficient substrate translocation, we constructed ClpP variants with amino acid substitutions in the N‐terminal region that forms the axial gates. We found that adoption of a β‐hairpin loop by this region and the integrity of the hydrophobic cluster at the base of this loop are necessary elements for the axial gate to efficiently translocate protein substrates. Analysis of ClpP variants from Bacillus subtilis suggested that the identified structural requirements of the axial channel for efficient translocation are conserved between Gram‐positive and Gram‐negative bacteria. These findings provide mechanistic insights into the activation of ClpP by ADEPs as well as the gating mechanism of the protease in the context of the ClpAP and ClpXP complexes.     

Cell therapy with autologous mesenchymal stromal cells in post-traumatic syringomyelia

Background aims

Recently, clinical studies show that cell therapy with mesenchymal stromal cells (MSCs) improves the sequelae chronically established in paraplegic patients, being necessary to know which of them can obtain better benefit.

Effects of salinity on the CO<Subscript>2</Subscript> permeation across lipid bilayer for microalgae biofixation: a molecular dynamics study

The continuous threat of increasing CO₂ concentration in the atmosphere has altered the carbon balance of our planet causing global climate change. Biological fixation of atmospheric CO₂ by unicellular microorganisms such as microalgae is a promising technology pursued extensively by researchers as a means for carbon capture. The study aimed to provide an atomic level of study that will demonstrate the effect of the salinity on the mechanism of CO₂ absorption across microalgae lipid bilayer. Molecular dynamics simulations were utilized to calculate the free energies of CO₂ molecule as it permeates inside the microalgae cell. In thermodynamics, the transport process of a molecule can be demonstrated through its free energy gradient. Thus, calculating the free energies of CO₂ molecule across microalgae lipid bilayer can elucidate the mechanisms of permeation processes. Four microalgae lipid bilayer structures were constructed that contains 128-DPPC (dipalmitoylphosphatidylcholine) lipid bilayer with 3640 water molecules with different NaCl concentrations: 0, 3, 13, and 19 NaCl molecules which correspond to a salinity level of 0, 50, 200, and 300 mM, respectively. The cavity insertion Widom method was used to calculate the free energy of CO₂ molecule along the lipid bilayer. The results demonstrated that the salinity does not affect the free energies significantly, thus, it does not hamper CO₂ transport across microalgae lipid membrane.