The phylogenetic position of Rhopalostroma as inferred from a polythetic approach

The xylariaceous genus Rhopalostroma comprises a small conglomerate of stromatic, angiosperm-associated pyrenomycetes, which have so far exclusively been reported from the palaeotropics, above all from tropical Africa and South Asia. Morphological and chemotaxonomic studies had suggested their close relationship to the genera Daldinia and Hypoxylon. However, those results were mainly based on herbarium specimens, and no molecular phylogenetic data were available on Rhopalostroma. During a foray in Côte d’Ivoire, fresh material of R. angolense was collected, cultured and studied by microscopic methods and by secondary metabolite profiling using high performance liquid chromatography coupled with diode array and mass spectrometric detection. In addition, ITS nrDNA sequences of the cultures were generated and compared to those of representative Xylariaceae taxa, to evaluate the phylogenetic affinities of this fungus. The results showed that R. angolense is closely related to the daldinoid Xylariaceae, and in particular to the predominantly neotropical genera Phylacia and Thamnomyces

Enzymatic Responses to Low-Intensity Radiation of Tritium

The present study considers a possible role of enzymatic reactions in the adaptive response of cells to the beta-emitting radionuclide tritium under conditions of low-dose exposures. Effects of tritiated water (HTO) on the reactions of bacterial luciferase and NAD(P)H:FMN-oxidoreductase, as well as a coupled system of these two reactions, were studied at radioactivity concentrations ≤ 200 MBq/L. Additionally, one of the simplest enzymatic reactions, photobiochemical proton transfer in Coelenteramide-containing Fluorescent Protein (CLM-FP), was also investigated. We found that HTO increased the activity of NAD(P)H:FMN-oxidoreductase at the initial stage of its reaction (by up to 230%); however, a rise of luciferase activity was moderate (<20%). The CLM-FP samples did not show any increase in the rate of the photobiochemical proton transfer under the exposure to HTO. The responses of the enzyme systems were compared to the ‘hormetic’ response of luminous marine bacterial cells studied earlier. We conclude that (1) the oxidoreductase reaction contributes significantly to the activation of the coupled enzyme system and bacterial cells by tritium, and (2) an increase in the organization level of biological systems promotes the hormesis phenomenon