Developmentally Arrested Precursors of Pontine Neurons Establish an Embryonic Blueprint of the Drosophila Central Complex

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Human–vegetation interactions during the Holocene in North America

Vegetation History and Archaeobotany - Between the initial colonization of North America and the European settlement period, Indigenous American land use practices shaped North American landscapes...     

Exon Inclusion Modulates Conformational Plasticity and Autoinhibition of the Intersectin 1 SH3A Domain

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Neutral mechanisms and niche differentiation in steady-state insular microbial communities revealed by single cell analysis

In completely insular microbial communities, evolution of community structure cannot be shaped by the immigration of new members. In addition, when those communities are run in steady state, the influence of environmental factors on their assembly is reduced. Therefore, one would expect similar community structures under steady-state conditions. Yet, in parallel setups, variability does occur. To reveal ecological mechanisms behind this phenomenon, five parallel reactors were studied at the single-cell level for about 100 generations and community structure variations were quantified by ecological measures. Whether community variability can be controlled was tested by implementing soft temperature stressors as potential synchronizers. The low slope of the lognormal rank-order abundance curves indicated a predominance of neutral mechanisms, i.e., where species identity plays no role. Variations in abundance ranks of subcommunities and increase in inter-community pairwise β-diversity over time support this. Niche differentiation was also observed, as indicated by steeper geometric-like rank-order abundance curves and increased numbers of correlations between abiotic and biotic parameters during initial adaptation and after disturbances. Still, neutral forces dominated community assembly. Our findings suggest that complex microbial communities in insular steady-state environments can be difficult to synchronize and maintained in their original or desired structure, as they are non-equilibrium systems.     

Coping with low water activities and osmotic stress in Acinetobacter baumannii: significance,current status and perspectives

Multidrug resistant (MDR) pathogens are one of the most pressing challenges of contemporary health care. Acinetobacter baumannii takes a predominant position, emphasized in 2017 by the World Health Organization. The increasing emergence of MDR strains strengthens the demand for new antimicrobials. Possible targets for such compounds might be proteins involved in resistance against low water activity environments, since A. baumannii is known for its pronounced resistance against desiccation stress. Despite the importance of desiccation resistance for persistence of this pathogen in hospitals, comparable studies and precise data on this topic are rare and the mechanisms involved are largely unknown. This review aims to give an overview of the studies performed so far and the current knowledge on genes and proteins important for desiccation survival. ‘Osmotic stress’ is not identical to ‘desiccation stress’, but the two share the response of bacteria to low water activities. Osmotic stress resistance is in general studied much better, and in recent years it turned out that accumulation of compatible solutes in A. baumannii comprises some special features such as the bifunctional enzyme MtlD synthesizing the unusual solute mannitol. Furthermore, the regulatory pathways, as understood today, will be discussed.     

Syndecans promote integrin-mediated adhesion of mesenchymal cells in two distinct pathways

Syndecans are transmembrane proteoglycans that support integrin-mediated adhesion. Well documented is the contribution of syndecan-4 that interacts through its heparan sulphate chains to promote focal adhesion formation in response to fibronectin domains. This process has requirements for integrin and signaling through the cytoplasmic domain of syndecan-4. Here an alternate pathway mediated by the extracellular domains of syndecans-2 and -4 is characterized that is independent of both heparan sulphate and syndecan signaling. This pathway is restricted to mesenchymal cells and was not seen in any epithelial cell line tested, apart from vascular endothelia. The syndecan ectodomains coated as substrates promoted integrin-dependent attachment, spreading and focal adhesion formation. Syndecan-4 null cells were competent, as were fibroblasts compromised in heparan sulphate synthesis that were unable to form focal adhesions in response to fibronectin. Consistent with actin cytoskeleton organization, the process required Rho-GTP and Rho kinase. While syndecan-2 and -4 ectodomains could both promote integrin-mediated adhesion, their pathways were distinct, as shown by competition assays. Evidence for an indirect interaction of beta1 integrin with both syndecan ectodomains was obtained, all of which suggests a distinct mechanism of integrin-mediated adhesion.     

Crystallographic and spectroscopic studies of peroxide-derived myoglobin compound II and occurrence of protonated FeIV O

High resolution crystal structures of myoglobin in the pH range 5.2-8.7 have been used as models for the peroxide-derived compound II intermediates in heme peroxidases and oxygenases. The observed Fe-O bond length (1.86-1.90 A) is consistent with that of a single bond. The compound II state of myoglobin in crystals was controlled by single-crystal microspectrophotometry before and after synchrotron data collection. We observe some radiation-induced changes in both compound II (resulting in intermediate H) and in the resting ferric state of myoglobin. These radiation-induced states are quite unstable, and compound II and ferric myoglobin are immediately regenerated through a short heating above the glass transition temperature (<1 s) of the crystals. It is unclear how this influences our compound II structures compared with the unaffected compound II, but some crystallographic data suggest that the influence on the Fe-O bond distance is minimal. Based on our crystallographic and spectroscopic data we suggest that for myoglobin the compound II intermediate consists of an Fe(IV)-O species with a single bond. The presence of Fe(IV) is indicated by a small isomer shift of delta = 0.07 mm/s from M?ssbauer spectroscopy. Earlier quantum refinements (crystallographic refinement where the molecular-mechanics potential is replaced by a quantum chemical calculation) and density functional theory calculations suggest that this intermediate H species is protonated.     

Rapid identification of malaria vaccine candidates based on alpha-helical coiled coil protein motif

To identify malaria antigens for vaccine development, we selected alpha-helical coiled coil domains of proteins predicted to be present in the parasite erythrocytic stage. The corresponding synthetic peptides are expected to mimic structurally "native" epitopes. Indeed the 95 chemically synthesized peptides were all specifically recognized by human immune sera, though at various prevalence. Peptide specific antibodies were obtained both by affinity-purification from malaria immune sera and by immunization of mice. These antibodies did not show significant cross reactions, i.e., they were specific for the original peptide, reacted with native parasite proteins in infected erythrocytes and several were active in inhibiting in vitro parasite growth. Circular dichroism studies indicated that the selected peptides assumed partial or high alpha-helical content. Thus, we demonstrate that the bioinformatics/chemical synthesis approach described here can lead to the rapid identification of molecules which target biologically active antibodies, thus identifying suitable vaccine candidates. This strategy can be, in principle, extended to vaccine discovery in a wide range of other pathogens.     

An intermediate step in the evolution of ATPases--the F1F0-ATPase from Acetobacterium woodii contains F-type and V-type rotor subunits and is capable of ATP synthesis

Previous preparations of the Na(+) F(1)F(0)-ATP synthase solubilized by Triton X-100 lacked some of the membrane-embedded motor subunits [Reidlinger J & Müller V (1994) Eur J Biochem233, 275-283]. To improve the subunit recovery, we revised our purification protocol. The ATP synthase was solubilized with dodecylmaltoside and further purified to apparent homogeneity by chromatographic techniques. The preparation contained, along with the F(1) subunits, the entire membrane-embedded motor with the stator subunits a and b, and the heterooligomeric c ring, which contained the V(1)V(0)-like subunit c(1) and the F(1)F(0)-like subunits c(2) and c(3). After incorporation into liposomes, ATP synthesis could be driven by an electrochemical sodium ion potential or a potassium ion diffusion potential, but not by a sodium ion potential. This is the first demonstration that an ATPase with a V(0)-F(0) hybrid motor is capable of ATP synthesis.