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Tome 145; National audience

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National audience; The microbial community on the surface of wood barrels used in winemaking was determined just before their first use, during first contact with wine, and some months after wine contact during successive racking at different steps of wine elaboration. Five microbial populations (total yeast, non-Saccharomyces yeast, lactic acid bacteria, acetic acid bacteria, and anaerobic and anaerobic tolerant Gram negative bacteria) were identified using 5 different selective culture media. Among each population, species and strains were identified using molecular tools such as the polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis, PCR-restriction fragment length polymorphism and pulsed field gel electrophoresis. At the laboratory scale, the risks of contamination were evaluated by wine inoculation trials and their impact on wine microbial population and chemical properties (volatile phenols and acetic acid) was determined. Before the first use and during the first wine contact, the microbial community on the barrel wood was mainly composed of basidiomycetes (Cryptococcus, Bulleromyces and Rhodotorula) and enterobacteria (Serratia sp. and Shigella sp.). After wine contact, these microorganisms became less and less detectable, which could be explained by their low ethanol resistance. However, some species could resist ethanol and remain detectable some weeks after the first barrelling. The ability of these species to degrade some wood components could affect the wine microbial consortium. In addition, since the first racking, the majority of microbial species found on the wood barrel surface was composed of major wine yeast (Saccharomyces cerevisiae) and bacterial (Oenococcus oeni) species, as well as spoilage organisms such as Brettanomyces bruxellensis, Pediococcus parvulus and Gluconobacter oxydans. Laboratory trials of contamination suggested that these residual populations were unable to cause wine alteration such as volatile phenol and acetic acid production. The microorganisms present on the wood surface could not modify the microbial steady state of wine containing some populations regulated by oenological practices (sulfating, racking) and also by microbial interactions between each species. When the microbial population was low as in the case after filtration or heat treatment, the contamination was more possible. In any cases, washing of barrels at each racking is strongly recommended to progressively eliminate the microorganisms that are adhered to the wood and to obtain an efficient microbial stability of the wine.

International audience; In Agaricus bisporus all cytological studies performed until now concerned the pseudohomothallic and bisporic var. bisporus. In the past 12 y two tetrasporic varieties have been described, the heterothallic var. burnettii and the homothallic var. eurotetrasporus. Our aim was to compare the behavior of the nuclei in the vegetative and reproductive cells of the three varieties with light microscopy (Feulgen and DAPI staining) and transmission electron microscopy. Most of the vegetative cells contained 3-5 nuclei in the three varieties. Nuclear migrations through the septum were detected. In the basidia relative locations of nuclei and vacuoles, meiotic spindle alignments, relative content of nuclear DNA and synaptonemal complexes were measured or observed. From the observation of numerous asynchronous second division of meiosis within basidia of var. bisporus and var. burnettii a new hypothesis emerges to explain the nonrandom distribution of the four meiotic products in the two spores of the bisporic basidia. Karyogamy and meiosis similarly occurred in the three varieties. In the case of A. bisporus var. eurotetrasporus this implies that the reproductive mode is sexual and therefore homothallic in the strict sense. The three different types of life cycles are described.

Diplôme : Dr. d'Universite

Agaricus specimens collected in France be- long to two novel entities resembling small forms of A. moelleri and A. xanthodermus, two common species in section Xanthodermatei. Molecular (IT11ITS2 DNA sequence) and morphological comparisons be- tween eight presumed similar taxa of the section sup- port the elevation of both entities to species rank. The new entities are described as A. parvitigrinus and A. xanthodermulus. They form a group with A. las- kibarii, a rare species also recently described from France, and A. californicus, a North-American spe- cies. The well known A. moelleri and A. xanthodermus are the most related species among the studied sam- ple. Like other species of the section, both new spe- cies have a phenolic odor and are probably toxic. Such specimens must have be taken for A. moelleri or A. xanthodermus or for specimens of A. pseudopraten- sis (Bohus) Wasser, which is the only small species of section Xantodermatei known in Europe except the tropical species A. endoxanthus Berk. et Br. that re- cently was found in Spain (Parra et al 2002) and the not well known Psalliota nigricans Velen. We com- pared morphological traits and sequences of the in- ternal transcribed spacers (ITS1 and ITS2) of the nu- clear rDNA of these small specimens with a group that included (i) three taxa morphologically similar: A. moelleri, A. xanthodermus, and A. xanthodermus var. macrosporus Aparici et Mahiques; (ii) the typically small sized species A. pseudopratensis; and (iii) two small to medium size species: A. laskibarii L.A. Parra et Arrillaga and A. californicus Peck. Agaricus laski- barii is a medium size species recently described from western France (Parra and Arrillaga 2002, Arrillaga Anabitarte 2004); A. californicus is a North American species that can be small (Peck 1895, Kerrigan 1986). Of the about 20 taxa of section Xanthodermatei se- quenced to date that will be treated separately in a further phylogenetic analysis of the section, only A. laskibarii and A. californicus have a sequence highly similar to those of the new entities. In addition to their small to medium size, this represents another reason to include them in the present study. We con- clude that our small specimens represent collections of two novel species described here as A. parvitigri- nus and A. xanthodermulus.

International audience

International audience

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International audience; For about 50 years, scientists have studied the biological activities of Macromycetes on different pathologies. In this article different fungal activities that reduce the effects of risk factors for cardiovascular diseases are reviewed. Among the 17 species tested on animals, 16 demonstrated at least one of the following activities: ability to reduce hypercholesterolemia or to cure dyslipoproteinemia, possibility to decrease arterial hypertension or hyperglycemia, and ability to cure disturbances in platelet aggregation.