3 research outputs found
Polyurethane–poly(2-hydroxyethyl methacrylate) semi- IPN–nanooxide composites
Two sets of hybrid polyurethane–poly(2-hydroxyethyl methacrylate) semi-interpenetrating polymer
network–nanooxide composites with 0.25 or 3 wt% nanosilica or nanoalumina functionalised with OH,
NH2 or CHLCH2 groups were prepared. A combination of atomic force microscopy, infrared spectroscopy,
thermally stimulated depolarisation current measurement, differential scanning calorimetry and creep rate
spectroscopy analysis of the nanostructure and properties of the composites was performed. The
pronounced dynamic heterogeneity and the strong impact of oxide additives, basically suppression of the
dynamics and temperature-dependent increasing modulus of elasticity, were observed. The effects correlated with either interfacial interactions (for silica) or the nanostructure (for alumina). A low oxide content strongly affected the matrix due to the formation of an unusual cross-linked, via double covalent hybridisation of three components, structure of the nanocomposites
Antibiotic Activity of Actinobacteria from the Digestive Tract of Millipede <i>Nedyopus dawydoffiae</i> (Diplopoda)
Because of the spread of drug resistance, it is necessary to look for new antibiotics that are effective against pathogenic microorganisms. The purpose of this study was to analyse the species composition of actinobacteria isolated from the digestive tract of the millipedes Nedyopus dawydoffiae and to determine their antimicrobial properties. Species identification was carried out on the basis of the morphological and culture properties and the sequence of the 16S rRNA gene. Actinobacteria were grown in different liquid media. Antibiotic properties were determined against some Gram-positive and Gram-negative bacteria as well as fungi. Of the 15 isolated strains, 13 have antibiotic activity against Gram-positive bacteria (including methicillin-resistant Staphylococcus aureus—MRSA) and fungi, but there was no antibiotic activity against Gram-negative test strains Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. It was established that antibiotic-producing actinobacteria belong to eight species of the genus Streptomyces. Depending on the nutrient medium, actinobacteria demonstrate different antimicrobial activities. As an example, S. hydrogenans shows that even strains selected in one population differ by the range of antimicrobial activity and the level of biosynthesis. Since the antibiotic production is considered as a feature for species competition in the microbiota community, the variability of antibiotic production among different strains of the same species is an adaptive characteristic for the competition in millipedes’ digestive tract community