Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Forest ecosystems have integral roles in climate stability, biodiversity and economic development. Soil stewardship is essential for sustainable forest management. Organic matter (OM) removal and soil compaction are key disturbances associated with forest harvesting, but their impacts on forest ecosystems are not well understood. Because microbiological processes regulate soil ecology and biogeochemistry, microbial community structure might serve as indicator of forest ecosystem status, revealing changes in nutrient and energy flow patterns before they have irreversible effects on long-term soil productivity. We applied massively parallel pyrosequencing of over 4.6 million ribosomal marker sequences to assess the impact of OM removal and soil compaction on bacterial and fungal communities in a field experiment replicated at six forest sites in British Columbia, Canada. More than a decade after harvesting, diversity and structure of soil bacterial and fungal communities remained significantly altered by harvesting disturbances, with individual taxonomic groups responding differentially to varied levels of the disturbances. Plant symbionts, like ectomycorrhizal fungi, and saprobic taxa, such as ascomycetes and actinomycetes, were among the most sensitive to harvesting disturbances. Given their significant ecological roles in forest development, the fate of these taxa might be critical for sustainability of forest ecosystems. Although abundant bacterial populations were ubiquitous, abundant fungal populations often revealed a patchy distribution, consistent with their higher sensitivity to the examined soil disturbances. These results establish a comprehensive inventory of bacterial and fungal community composition in northern coniferous forests and demonstrate the long-term response of their structure to key disturbances associated with forest harvesting. The ISME Journal (2012) 6, 2199-2218; doi:10.1038/ismej.2012.84; published online 2 August 2012
ISSN: 1751-7362

hal-01546179
https://hal.archives-ouvertes.fr/hal-01546179
DOI : 10.1038/ismej.2012.84

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
We carried out a soil sampling survey in September 2008 in central Cayenne, French Guiana, using molecular methods to assess the presence of the dimorphic fungus Histoplasma capsulatum. Four of the 31 samples collected (12.9 %) tested positive by PCR, with confirmation of the result by DNA sequencing. H. capsulatum is therefore present in urban environments in French Guiana. These results provide additional support for the primary prophylaxis of AIDS-related histoplasmosis in French Guiana
ISSN: 0301-486X

hal-01349668
https://hal.archives-ouvertes.fr/hal-01349668
https://hal.archives-ouvertes.fr/hal-01349668/file/Article%20Histo%20Cayenne%20R2.pdf
DOI : 10.1007/s11046-012-9550-y

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
Naegleria fowleri is found in most geothermal baths of Guadeloupe and has been responsible for the death of a 9-year-old boy who swam in one of these baths in 2008. We wanted to determine the origin for the presence of this amoeba in the water.Water samples were taken at the origin of the geothermal sources and at the arrival in the baths. After filtration, cultures were made and the number of Naegleria present was determined using the most probable number method. Soil samples collected in the proximity of the baths were also tested for the presence of thermophilic amoebae. The species identification was obtained by PCR. During three consecutivemonths, no Naegleria could be found at the origin of any geothermal source tested. In contrast, N. fowleri was isolated at least once in all baths at the arrival of the water, except one. Thermophilic amoebae could be found in each soil sample, especially near the baths located at a lower altitude, but N. fowleri was only isolated near two baths, which were also the baths most often contaminated with this species. So it appears that the contamination of the water with N. fowleri occurs after emerging from the geothermal source when the water runs over the soil. Therefore, it should be possible to reduce the concentration of N. fowleri in thegeothermal baths of Guadeloupe to for example less than 1 N. fowleri/10 L by installing a pipeline between the geothermal sources and the baths and by preventing flooding water from entering the baths after rainfall. By taking these measures, we were able to eliminate N. fowleri from a poollocated inside a reeducation clinic.
ISSN: 0932-0113

pasteur-01136739
https://hal-riip.archives-ouvertes.fr/pasteur-01136739
DOI : 10.1007/s00436-014-4197-x.
PUBMED : 25352239

Éditeur(s) : HAL CCSD
Résumé : Background and objectives.[br/] Dairy propionibacteria are isolated from various ecological niches, including soil, grass, silage, rumen, raw milk and dairy plants, showing great adaptability and robustness. Used as ripening starters in Swiss type cheeses, these food grade bacteria are described as nutraceutical producers and they release into the external medium short chain fatty acids (SCFA), folic acid, cobalamin and the bifidogenic 1,4- dihydroxy-2-naphthoic acid (DHNA). These compounds are known to play a pivotal role in the modulation of intestinal physiology through diet. Considering the pro-apoptotic potential of some of these metabolites, we investigated the potential of dairy products fermented by the main species, Propionibacterium freudenreichii, to prevent colon carcinogenesis. Methods.[br/] We developed a new fermented milk. Taking advantage of milk fractions, high and stable populations of P. freudenreichii were obtained in this product. It was tested in vitro on gastric HGT-1 and colic HT-29 cells with respect to the typical hallmarks of apoptosis. In vivo, the fermented milk was evaluated in piglets with respect to general health parameters and in human microbiota-associated rats, treated or not with dimethylhydrazine (DMH), with respect to intestinal proliferation and apoptosis. Results. Fermented milk induced cell death in both gastric and colon cancer cells. Cellular and molecular characterization of cells dying in response to SCFA treatment revealed cell cycle arrest, drop in intracellular ATP, depolarization of mitochondria, translocation of key apoptosis proteins, processing of caspases and fragmentation of the nucleus. Interestingly, the new fermented milk was shown to potentiate the cytotoxic effect of molecules used in cancer chemotherapy. In accordance, it modulated expression of key apoptotic proteins. In vivo, the fermented milk was evaluated in piglets. Daily oral gavage led to high colic P. freudenreichii populations, to modulation of the intestinal microbiota and modulation of intestinal cytokines. Promotion of piglets’ growth also revealed general probiotic effects of fermented milk. Considering that propionibacteria were metabolically active in the intestine, we further investigated their impact on colon carcinogenesis (induced by dimethylhydrazine, DMH) in human microbiota-associated rats. Consumption of selected strains of propionibacteria resulted in enhanced apoptotic depletion of DMH damaged epithelial cells, yet had no effect on neither proliferation nor apoptosis in healthy rats. Conclusions and perspectives.[br/] These results open new perspectives in the field of colon cancer cells prevention and/or treatment. The synergy with pro-apoptotic chemotherapy molecules suggests that such a fermented product may be proposed as a food supplement to enhance the effects of anticancer treatments.
colloque international « Nutrition and Cancer : Hot topics from biology to public health issues »
Paris, France

hal-01190452
https://hal.archives-ouvertes.fr/hal-01190452
PRODINRA : 201853