Biological activities of endozoic fungi isolated from Biomphalaria alexandrina snails maintained in different environmental conditions

This work aims at studying Biomphalaria alexandrina snails as a source of bioactive compounds. Adult snails were maintained in plastic, mud and cement matrices. Three groups were prepared; under normal laboratory conditions, in slightly low pH conditions, and in high temperature (30°C) conditions. Nine fungal species were isolated from soft tissues of snails. Ethyl acetate and acetone extracts were prepared from each fungal species, and their biological activities were investigated. Paecilomyces variotii extracts were the most effective as antimicrobial agents, while acetone extract of Trichoderma harzianum showed high antioxidant activity. Acetone extracts of Penicillium islandicum and Aspergillus niger were highly active against hepatocellular carcinoma (HepG2) cell lines. Gas chromatography/mass spectrometry analysis of the five effective extracts showed the presence of various compounds. B. alexandrina snails may be regarded as a newly discovered source of beneficial compounds through the metabolites produced by their endozoic fungal strains.     

Extracting the bulk effective parameters of a metamaterial via the scattering from a single planar array of particles

In this paper we present a method for retrieving the effective parameters of a metamaterial composed of a regular rectangular orthorhombic lattice of linear biaxially anisotropic particles suspended in free space. By assuming the point–dipole interaction approximation, equations are derived which extract the electric and magnetic polarizabilities of the individual particles given the measured or simulated scattering parameters of a single planar array of particles. These results are in turn substituted into the Clausius–Mossotti equations to find the bulk effective permittivity and effective permeability. To demonstrate our approach, the extraction method is applied to a metamaterial consisting of a cubic arrangement of magnetodielectric spheres using the scattering parameters obtained by simulating the structure with Ansoft HFSS. Our results show good agreement with a known analytical solution at frequencies in which the Clausius–Mossotti approximation is valid.     

Comparison of a novel MPN method against the yeast extract agar (YEA) pour plate method for the enumeration of heterotrophic bacteria from drinking water

This study compared the Quanti-Disc most probable number (MPN) test for heterotrophic bacteria from drinking water with the widely used yeast extract agar (YEA) pour plate method. The Quanti-Disc test module contains 50 reaction wells in which a medium has been pre-deposited. The medium contains a suite of three fluorogenic enzyme substrates selected for the detection of enzymes expressed widely by heterotrophic bacteria. The MPN of heterotrophic bacteria is calculated from the number of fluorescing reaction wells after incubation of a sample. Quanti-Disc and the YEA pour plate method were compared according to guidance on comparing methods given in United Kingdom national guidance and ISO 17994:2004. The two methods were also challenged with reference strains and isolates of heterotrophic bacteria from drinking water. This indicated that heterotrophic bacteria commonly encountered in drinking water are detected by both the YEA pour plate method and Quanti-Disc. Analysis of data from split water samples (723 for 37 degrees C tests and 872 for 22 degrees C tests) from nine geographically diverse laboratories in England and Wales demonstrated that the Quanti-Disc method is equivalent to the YEA pour plate method for the analysis of heterotrophic bacteria from drinking and similar waters at 37 degrees C, and superior to YEA for the analysis at 22 degrees C. The Quanti-Disc method is a simple and efficient alternative method for the enumeration of heterotrophic bacteria from drinking water.