Identification of tet(M) in two Lactococcus lactis strains isolated from a Spanish traditional starter-free cheese made of raw milk and conjugative transfer of tetracycline resistance to lactococci and enterococci

Specific PCR and sequencing showed that a tet(M) gene was present in two tetracycline-resistant Lactococcus lactis strains isolated from a raw milk, starter-free cheese. Hybridisation experiments using as a probe an internal segment of the gene obtained by PCR associated tet(M) with plasmids of around the same size (30 kbp) in both strains. Molecular analysis of the tetracycline resistance loci, including the upstream and downstream regions of the genes, showed them to be identical to one other and to the tet(M) encoded by the conjugative transposon Tn916. Amplification of Tn916-derived segments suggested the transposon was complete in the two L. lactis strains. Further, curing of the tetracycline resistance was accompanied by a reduction in size of the plasmids comparable to that expected for Tn916. Tetracycline resistance could be transferred by conjugation to plasmid-free Lactococcus and Enterococcus strains. However, no plasmid DNA was detected among the transconjugants while both tet(M) and transposon-related sequences were amplified by PCR. This suggested that only the transposon was mobilized.     

Revision of ochratoxin a production capacity by the main species of Aspergillus section Circumdati. Aspergillus steynii revealed as the main risk of OTA contamination

Ochratoxin A (OTA) is a highly toxigenic mycotoxin commonly present in a number of diverse agroproducts. Aspergillus Section Circumdati includes some of the most important OTA-producing species: Aspergillus ochraceus, Aspergillus elegans and the recently described Aspergillus steynii and Aspergillus westerdijkiae. In this work, OTA production by several strains of these four species from diverse origins and food matrices was examined. Identification of all the strains was carried out by specific PCR assays. The strains were cultivated in CYA solid medium and OTA was measured by HLPC. This study demonstrated for the first time the high capacity of A. steynii strains to produce OTA at higher levels than A. westerdijkiae,A. ochraceus and A. elegans strains showed low levels or no production at all. In conclusion, the results of this study suggest that the occurrence of A. steynii and A. westerdijkiae might represent the major potential risk for OTA contamination due to their high production and the diversity of commodities that these species may contaminate.     

Scientists' performance and consolidation of research teams in Biology and Biomedicine at the Spanish Council for Scientific Research

Summary Empirical evidence is given on how membership in a consolidated, well-established research team provides researchers with some competitive advantage as compared to their colleagues in non-consolidated teams. Data were obtained from a survey of researchers ascribed to the 'Biology and Biomedicine' area of the Spanish Council for Scientific Research, as well as from their curricula vitae. One quarter of the scientists work as members of teams in the process of consolidation. Our findings illustrate the importance, for the development and consolidation of research teams, of the availability of a minimum number of researchers with a permanent position and of a minimum number of support staff and non-staff personnel (mainly post-doctoral fellows). Consolidation of research teams has a clear influence on the more academic-oriented quantitative indicators of the scientific activity of individuals. Researchers belonging to consolidated teams perform quantitatively better than their colleagues in terms of the number of articles published in journals covered in the Journal Citation Reports, but not in terms of the impact of these publications. Consolidation favours publication, but not patenting, and it also has a positive effect on the academic prestige of scientists and on their capacity to train new researchers. It does not significantly foster participation in funded R&D projects, nor does it influence the establishment of international collaborations. Impact is influenced to a remarkable degree by seniority and professional background, and is significantly greater for young scientists who have spent time abroad at prestigious research laboratories.     

Energy release behind the Jouguet point during detonation of plasticized PETN from the results of experiments by the T-20 method

The trajectory of motion of a copper shell, the velocity of its flight, and the pressure of the explosion products on the inside of the copper shell were simulated. It was found that there is a significant difference in pressure behavior between experiments and calculations performed using the standard equations of state of explosives and explosion products. Most likely, there is a significant contribution of kinetic processes to the energy release behind the Jouguet point. In this case, the conversion of explosives to explosion products apparently include not only exothermic reactions but also endothermic processes.     

Inhibitors against Fungal Cell Wall Remodeling Enzymes

Fungal β‐1,3‐glucan glucanosyltransferases are glucan‐remodeling enzymes that play important roles in cell wall integrity, and are essential for the viability of pathogenic fungi and yeasts. As such, they are considered possible drug targets, although inhibitors of this class of enzymes have not yet been reported. Herein we report a multidisciplinary approach based on a structure‐guided design using a highly conserved transglycosylase from Sacharomyces cerevisiae, that leads to carbohydrate derivatives with high affinity for Aspergillus fumigatus Gel4. We demonstrate by X‐ray crystallography that the compounds bind in the active site of Gas2/Gel4 and interact with the catalytic machinery. The topological analysis of noncovalent interactions demonstrates that the combination of a triazole with positively charged aromatic moieties are important for optimal interactions with Gas2/Gel4 through unusual pyridinium cation–π and face‐to‐face π–π interactions. The lead compound is capable of inhibiting AfGel4 with an IC₅₀ value of 42 μm .     

Simulation of liquid micro-jet in free expanding high-speed co-flowing gas streams

We present the development of an experimentally validated computational fluid dynamics model for liquid micro jets. Such jets are produced by focusing hydrodynamic momentum from a co-flowing sheath of gas on a liquid stream in a nozzle. The numerical model based on laminar two-phase, Newtonian, compressible Navier–Stokes equations is solved with finite volume method, where the phase interface is treated by the volume of fluid approach. A mixture model of the two-phase system is solved in axisymmetry using?~?300,000 finite volumes, while ensuring mesh independence with the finite volumes of the size 0.25 µm in the vicinity of the jet and drops. The numerical model is evaluated by comparing jet diameters and jet lengths obtained experimentally and from scaling analysis. They are not affected by the strong temperature and viscosity changes in the focusing gas while expanding at nozzle outlet. A range of gas and liquid-operating parameters is investigated numerically to understand their influence on the jet performance. The study is performed for gas and liquid Reynolds numbers in the range 17–1222 and 110–215, and Weber numbers in the range 3–320, respectively. A reasonably good agreement between experimental and scaling results is found for the range of operating parameters never tackled before. This study provides a basis for further computational designs as well as adjustments of the operating conditions for specific liquids and gases.