Targeted discovery of tetrapeptides and cyclic polyketide-peptide hybrids from a fungal antagonist of farming termites

Herein, we report the targeted isolation and characterization of four linear nonribosomally synthesized tetrapeptides (pseudoxylaramide A–D) and two cyclic nonribosomal peptide synthetase- polyketide synthase-derived natural products (xylacremolide A and B) from the termite-associated stowaway fungus Pseudoxylaria sp. X187. The fungal strain was prioritized for further metabolic analysis based on its taxonomical position and morphological and bioassay data. Metabolic data were dereplicated based on high-resolution tandem mass spectrometry data and global molecular networking analysis. The structure of all six new natural products was elucidated based on a combination of 1D and 2D NMR analysis, Marfey’s analysis and X-ray crystallography.The Deutsche Forschungsgemeinschaft (DFG)https://chemistry-europe.onlinelibrary.wiley.com/journal/14397633am2020BiochemistryGeneticsMicrobiology and Plant Patholog

Adaptations of Pseudoxylaria towards a comb-associated lifestyle in fungus-farming termite colonies

DATA AVAILABILITY: Supporting Information of this article is free of charge and contains list of accession numbers of sequences used for analysis, phylogenetic trees, cultivation studies including co-cultivation, analyses of genomic and metabolomic data, NMR and MS-data of isolated metabolites and data of insect feeding studies including statistical analyses.Characterizing ancient clades of fungal symbionts is necessary for understanding the evolutionary process underlying symbiosis development. In this study, we investigated a distinct subgeneric taxon of Xylaria (Xylariaceae), named Pseudoxylaria, whose members have solely been isolated from the fungus garden of farming termites. Pseudoxylaria are inconspicuously present in active fungus gardens of termite colonies and only emerge in the form of vegetative stromata, when the fungus comb is no longer attended (“sit and wait” strategy). Insights into the genomic and metabolic consequences of their association, however, have remained sparse. Capitalizing on viable Pseudoxylaria cultures from different termite colonies, we obtained genomes of seven and transcriptomes of two Pseudoxylaria isolates. Using a whole-genome-based comparison with free-living members of the genus Xylaria, we document that the association has been accompanied by significant reductions in genome size, protein-coding gene content, and reduced functional capacities related to oxidative lignin degradation, oxidative stress responses and secondary metabolite production. Functional studies based on growth assays and fungus-fungus co-cultivations, coupled with isotope fractionation analysis, showed that Pseudoxylaria only moderately antagonizes growth of the termite food fungus Termitomyces, and instead extracts nutrients from the food fungus biomass for its own growth. We also uncovered that Pseudoxylaria is still capable of producing structurally unique metabolites, which was exemplified by the isolation of two novel metabolites, and that the natural product repertoire correlated with antimicrobial and insect antifeedant activity.The German Research Foundation (DFG, Deutsche Forschungsgemeinschaft), the Germany´s Excellence Strategy, the European Research Council and The Danish Council for Independent Research. Open Access funding enabled and organized by Projekt DEAL.https://www.nature.com/ismejBiochemistryGeneticsMicrobiology and Plant Patholog

Spatiotemporal dynamics of word retrieval in speech production revealed by cortical high-frequency band activity.

Word retrieval is core to language production and relies on complementary processes: the rapid activation of lexical and conceptual representations and word selection, which chooses the correct word among semantically related competitors. Lexical and conceptual activation is measured by semantic priming. In contrast, word selection is indexed by semantic interference and is hampered in semantically homogeneous (HOM) contexts. We examined the spatiotemporal dynamics of these complementary processes in a picture naming task with blocks of semantically heterogeneous (HET) or HOM stimuli. We used electrocorticography data obtained from frontal and temporal cortices, permitting detailed spatiotemporal analysis of word retrieval processes. A semantic interference effect was observed with naming latencies longer in HOM versus HET blocks. Cortical response strength as indexed by high-frequency band (HFB) activity (70-150 Hz) amplitude revealed effects linked to lexical-semantic activation and word selection observed in widespread regions of the cortical mantle. Depending on the subsecond timing and cortical region, HFB indexed semantic interference (i.e., more activity in HOM than HET blocks) or semantic priming effects (i.e., more activity in HET than HOM blocks). These effects overlapped in time and space in the left posterior inferior temporal gyrus and the left prefrontal cortex. The data do not support a modular view of word retrieval in speech production but rather support substantial overlap of lexical-semantic activation and word selection mechanisms in the brain

Baseline Chest Computed Tomography as Standard of Care in High-Risk Hematology Patients

Baseline chest computed tomography (BCT) in high-risk hematology patients allows for the early diagnosis of invasive pulmonary aspergillosis (IPA). The distribution of BCT implementation in hematology departments and impact on outcome is unknown. A web-based questionnaire was designed. International scientific bodies were invited. The estimated numbers of annually treated hematology patients, chest imaging timepoints and techniques, IPA rates, and follow-up imaging were assessed. In total, 142 physicians from 43 countries participated. The specialties included infectious diseases (n = 69; 49%), hematology (n = 68; 48%), and others (n = 41; 29%). BCT was performed in 57% (n = 54) of 92 hospitals. Upon the diagnosis of malignancy or admission, 48% and 24% performed BCT, respectively, and X-ray was performed in 48% and 69%, respectively. BCT was more often used in hematopoietic cell transplantation and in relapsed acute leukemia. European centers performed BCT in 59% and non-European centers in 53%. Median estimated IPA rate was 8% and did not differ between BCT (9%; IQR 5-15%) and non-BCT centers (7%; IQR 5-10%) (p = 0.69). Follow-up computed tomography (CT) for IPA was performed in 98% (n = 90) of centers. In high-risk hematology patients, baseline CT is becoming a standard-of-care. Chest X-ray, while inferior, is still widely used. Randomized, controlled trials are needed to investigate the impact of BCT on patient outcome

Microstructure, mechanical and thermo-physical properties of CVD TiCxN1-x coatings on cemented carbide substrates grown with C2H6 as C feeding precursor

The established industrial processes used for the growth of TiCxN1-x coatings by chemical vapor deposition (CVD) suffer from substantial limitations, either in regard of brittle phase formation or restriction in the C/(C + N) ratio. Using the alternative C precursor C2H6 allows to overcome these issues. Thus, within this work, the microstructure, phase composition, micro-mechanical and thermo-physical properties of CVD TiCxN1-x coatings grown with C2H6 were investigated. Through adjustment of the C2H6 and N2 flow in the feed gas, the C/(C + N) ratio in the coatings was varied between pure TiN and TiC0.80N0.20. All coatings are characterized by a single-phase face centered cubic structure. The 〈110〉 fiber texture present in all coatings becomes more pronounced with increasing C content. None of the investigated coatings showed thermal cracks on the surface. The thermal conductivity decreases with addition of C from 45 ± 5 W/mK in TiN to 32 ± 3 W/mK in all ternary TiCxN1-x coatings. TiC0.47N0.53 exhibits the highest hardness (30.0 ± 1.4 GPa), while TiC0.63N0.36 turned out as the stiffest coating with a Young's modulus of 576 ± 23 GPa. The fracture stress σF and toughness KIC are superior in coatings with moderate C and N content, with TiC0.63N0.37 being the strongest (σF = 7.7 ± 0.4 GPa) and TiC0.47N0.53 (KIC = 4.4 ± 0.3 MPa m1/2) the toughest within this series. Coatings with moderate to high C content were found to exhibit a microstructure provoking a lower thermal conductivity and improved mechanical properties compared to those with a low C/(C + N) ratio

In-situ investigation of the oxidation behavior of metastable CVD Ti1−xAlxNTi_{1-x}Al_{x}N using a novel combination of synchrotron radiation XRD and DSC

Ti1-$_x$Al$_x$N hard coatings deposited by chemical vapor deposition (CVD) have attracted much attention recentlydue to their extraordinary nanolamellar microstructure and outstanding performance observed in metal cuttingoperations. Several published reports suggest further that CVD-Ti1-$_x$Al$_x$N exhibits an increased thermal stabilityand high temperature oxidation resistance when compared to state-of-the-art physical vapor deposited Ti-xAlxN.However, the exact mechanisms underlying the oxidation of this coating system are not thoroughly understoodyet. Thus within this work, the thermal stability and oxidation resistance of a powdered nanolamellar CVD-Ti1-$_x$Al$_x$N coating have been investigated at the synchrotron radiation facility applying a novel in-situ experimentalapproach. The sample was annealed in air between 100 and 1400 °C and 2D X-ray diffraction patterns wererecorded simultaneously with the differential scanning calorimetric signal. The obtained diffraction data wassuccessively analyzed using sequential Rietveld refinement, yielding the temperature-dependent phase composition.By combining this method with the differential scanning calorimetric data, it was possible to preciselytrack the onset and progress of chemical reactions. The results show that the different phases present in thesample oxidize individually, with the oxidation stability strongly depending on the Al-content. Further it wasfound that when Ti1-$_x$Al$_x$N spinodally decomposes in air, the formed TiN oxidizes directly after its formationwhile AlN retains its chemical stability. The present work provides not only a detailed insight into the thermalstability and oxidation resistance of CVD-Ti1-$_x$Al$_x$N but also proves the outstanding ability of the used method foranalyzing metastable coatings systems

Evolution of the microstructure of sputter deposited TaAlON thin films with increasing oxygen partial pressure

Recently, quaternary oxynitrides of transition metals and aluminum have attracted increasing interest due to their tunable properties. Within the present work, a series of TaAl(O)N films was sputter deposited using constant nitrogen and varying oxygen partial pressures. The films were grown from single element Ta and Al targets. The deposition parameters were adjusted to obtain a Ta/Al atomic ratio of ~50/50 for the oxygen-free film and were held constant for the following depositions, with the exception of the increasing oxygen partial pressure and compensatory decreasing argon partial pressure. Elastic recoil detection analysis revealed oxygen contents of up to ~26 at.%, while the nitrogen content decreased from ~47 at.% in the oxygen-free film to ~35 at.% in the film with the highest oxygen content, resulting in a significant decrease of the metal/non-metal ratio with increasing oxygen partial pressure. The micro- and bonding structures of the films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. All films exhibited a dominating face-centered cubic TaN-based structure with indications for additional nanocrystalline and amorphous phase fractions in the oxygen containing films. In addition, the mechanical properties were evaluated by nanoindentation, yielding a decreasing hardness and elastic modulus with increasing oxygen content.peerReviewe

Thermal stability of a cathodic arc evaporated Cr0.74_{0.74}Ta0.26_{0.26}N coating

CrTaN coatings have recently received increasing industrial interest due to their combination of high hardness, promising fracture toughness and excellent oxidation resistance. However, up to now no thorough investigation on the thermal stability of this coating system is available. Thus, within this work, the evolution of the microstructure and phase composition of an arc evaporated CrTaN coating were illuminated in inert atmosphere up to 1400°C. The coating crystallizes in an fcc-Cr$_{0.74}$Ta$_{0.26}$N solid solution with a preferred orientation. Alternating Cr-enriched and Ta-enriched layers are identified in the cross-section of the as-deposited coating, which arise from the three-fold rotation during deposition. In-situ high energy X-ray diffraction showed that powdered CrTaN is stable in inert atmosphere up to ∼1250°C, where fcc-Cr$_x$Ta$_{1-x}$N starts to transform into t-Cr$_{1.2}$Ta$_{0.8}$N. Upon further increasing the temperature to values exceeding 1300°C, h-Cr$_2$N and h-Ta$_5$N$_4$ start to form. Vacuum annealing of a CrTaN coating on a sapphire substrate at 1000°C results in the homogenization of the synthesis-related compositional fluctuations. While still maintaining the fcc-Cr$_x$Ta$_{1-x}$N solid solution, a texture change to a preferred orientation is observed after annealing at 1270°C. An annealing treatment at 1300°C results in the formation of t-Cr$_{1.2}$Ta$_{0.8}$N in addition to the fcc-Cr$_{1-x}$Ta$_x$N

Decomposition of CrN induced by laser-assisted atom probe tomography

It is known that measurement parameters can significantly influence the elemental composition determined by atom probe tomography (APT). Especially results obtained by laser-assisted APT show a strong effect of the laser pulse energy on the apparent elemental composition. Within this study laser-assisted APT experiments were performed on Cr0.51N0.49 and thermally more stable (Cr0.47Al0.53)0.49N0.51, comparing two different base tem-peratures (i.e. 15 and 60 K), laser wavelengths (i.e. 532 and 355 nm) and systematically modified laser pulse energies. Absolute chemical compositions from laser-assisted APT were compared to data obtained from ion beam analysis. The deduced elemental composition of CrN exhibited a strong increase of the Cr content when the laser pulse energy was increased for both laser wavelengths. For low laser pulse energies Cr, CrN, N and N2 ions were identified, while the amount of detected Cr ions increased and the amount of N ions strongly decreased at higher laser pulse energies. Further, increased detection of more complex Cr-containing ions such as Cr2N at the expense of CrN was observed at higher pulse energies. At the highest pulse energy levels used within this work, the resulting Cr content was > 80 at%, dominated by the amount of detected elemental Cr ions. The change of the mass spectrum of the detected ions with increasing laser pulse energy provides evidence that high laser pulse energies initiate the decomposition of CrN during the APT measurement, consistent with the known thermal decomposition path into Cr2N and subsequently into Cr and gaseous N. In contrast, variation of the laser pulse energy for the thermally more stable CrAlN resulted only in a slight increase of Cr and a decrease of the resulting concentrations of Al and N with increasing laser pulse energy and no change in the type of detected ions. In conclusion, within the present study, the decomposition of a coating material with low thermal stability induced by laser-assisted APT was reported for the first time, emphasizing the importance of the selection of suitable measurement parameters for metastable materials, which are prone to thermal decomposition

Influence of multiple detection events on compositional accuracy of TiN coatings in atom probe tomography

The accuracy of composition measurements by atom probe tomography is often dependent on the selected operation mode as well as the applied measurement parameters. The detected hit characteristics, distinguishing between single and multiple events, along with the electric field, are also affected by parameter selection. In this study, atom probe tomography experiments were performed on a stoichiometric TiN coating in voltage as well as in laser-assisted mode with systematically varied laser pulse energies. The observed elemental compositions were compared with complementary ion beam analysis measurements. The influence of multiple detection events was investigated by two approaches: I) A modified local electrode served as a hardware filter, reducing multiple detection events from 78.8 % to 41.9 % and from 40.9 % to 5.6 % using voltage mode and laser-assisted APT (0.6 nJ), respectively, and II) unfiltered datasets were analyzed by data post processing. The latter allowed the study of ion species, particularly of emerging complex molecular ions associated with dissociation processes. Additionally, average electric fields were estimated and spatial considerations were made to investigate the evolution of charge state ratios and hit characteristics during the measurement. Filtering the measurements significantly improved the elemental accuracy. In voltage mode, hardware and software filtering reduced the discrepancy between reference and observed composition from 3.8 at.% to 2.1 at.% and 0.1 at.% within uncertainty limits. In laser-assisted mode, higher laser pulse energy increased the difference between unfiltered data and the reference composition, from 1.4 at.% (0.1 nJ) to 8.1 at.% (2.0 nJ). Ion species analysis of the datasets shows an increasing presence of complex ions (Ti2N) with raising laser pulse energy. Electric field studies reveal a decline from 40 V/nm in voltage mode to 36 V/nm applying a high laser pulse energy of 2.0 nJ, indicating insufficient field strength for neutral nitrogen re-ionization