Les cyanobactéries dans les environnements froids

Cyanobacteria evolved under the harsh conditions of the Precambrian and their modern representatives retain a remarkable ability to adapt to and survive within extreme conditions. They dominate terrestrial and freshwater cold ecosystems of the Arctic, Antarctic and alpine regions, even though they do not seem to be specifically adapted to optimal growth at low temperatures. They play a major ecological role as they often are primary colonisers of substrates and major primary producers in these ecosystems. The application of molecular tools in combination with classic morphological techniques has begun to provide new insights into the real diversity of cyanobacteria and their biogeographical distribution in cold environments. Our survey of recent studies suggests complex distributional patterns of cyanobacteria, with cosmopolitan, endemic, and habitat-specific genotypes. This ongoing research will help to identify specific geographical areas that have unique microbial communities. However, many more studies are needed to unravel the enormous diversity of cyanobacteria and to better define their biogeographical patterns in cold environments. This is an urgent task in view of the climatic changes that will undoubtedly alter the structure and functioning of microbial communities in polar and alpine ecosystems.AMBI

Assessment of wheat grain fractionation processes involvement in the product contamination with DON

International audienc

Assessment of wheat grain fractionation processes involvement in the product contamination with DON

International audienc

Multilocus sequence analysis of root nodule isolates from Lotus arabicus (Senegal), Lotus creticus, Argyrolobium uniflorum and Medicago sativa (Tunisia) and description of Ensifer numidicus sp nov and Ensifer garamanticus sp. nov.

Nine isolates from Argyrolobium uniflorum, Lotus creticus, Medicago sativa (Tunisia) and Lotus arabicus (Senegal) were analysed by multilocus sequence analysis (MLSA) of five housekeeping genes (recA, atpD, glnA, gltA and thrC), the 16S rRNA gene and the nodulation gene nodA. Analysis of the individual and concatenated gene sequences demonstrated that the nine new strains constituted three stable, well-supported (bootstrap and gene sequence similarity values) monophyletic clusters, A, B and C, all belonging to the branch of the genus Ensifer, regardless of the phylogenetic reconstruction method used (maximum likelihood, maximum-parsimony, neighbour-joining). The three groups were further characterized by API 100 auxanographic tests, host specificity and nodA gene sequence analysis. On the basis of these data, clusters A and C are suggested as representing two novel species within the genus Ensifer, for which the names Ensifer numidicus sp. nov. (type strain ORS 1407(T) = LMG 24690(T) = CIP 109850(T)) and Ensifer garamanticus sp. nov. (type strain ORS 1400(T) = LMG 24692(T) = CIP 109916(T)) are proposed. The cluster B strains were assigned to Ensifer adhaerens genomovar A