Le REBENT-II Bretagne . Surveillance du Benthos du littoral breton. Année 2019

Ce « Rapport final » dresse le bilan des données REBENT acquises en 2019, pour des habitats benthiques exclusivement rocheu

Le REBENT-II Bretagne . Surveillance du Benthos du littoral breton. Année 2020

Ce « Rapport final » dresse le bilan des données REBENT acquises en 2020, pour des habitats benthiques exclusivement rocheux (Fig 1) ; en effet, les autres habitats sont désormais suivis via les dispositifs DCE et DCSMM (via des financements Agence de l’Eau Loire-Bretagne)

Le REBENT-II Bretagne . Surveillance du Benthos du littoral breton. Année 2018

Ce « Rapport final » dresse le bilan des données REBENT acquises en 201

Evolution of the terminal regions of the streptomyces linear chromosome

International audienceComparative analysis of the Streptomyces chromosome sequences, between Streptomyces coelicolor, Streptomyces avermitilis, and Streptomyces ambofaciens ATCC23877 (whose partial sequence is released in this study), revealed a highly compartmentalized genetic organization of their genome. Indeed, despite the presence of specific genomic islands, the central part of the chromosome appears highly syntenic. In contrast, the chromosome of each species exhibits large species-specific terminal regions (from 753 to 1,393 kb), even when considering closely related species (S. ambofaciens and S. coelicolor). Interestingly, the size of the central conserved region between species decreases as the phylogenetic distance between them increases, whereas the specific terminal fraction reciprocally increases in size. Between highly syntenic central regions and species-specific chromosomal parts, there is a notable degeneration of synteny due to frequent insertions/deletions. This reveals a massive and constant genomic flux (from lateral gene transfer and DNA rearrangements) affecting the terminal contingency regions. We speculate that a gradient of recombination rate (i.e., insertion/deletion events) toward the extremities is the force driving the exclusion of essential genes from the terminal regions (i.e., chromosome compartmentalization) and generating a fast gene turnover for strong adaptation capabilitie

Intraspecific Variability of the Terminal Inverted Repeats of the Linear Chromosome of Streptomyces ambofaciens

The sequences of the terminal inverted repeats (TIRs) ending the linear chromosomal DNA of two Streptomyces ambofaciens strains, ATCC23877 and DSM40697 (198 kb and 213 kb, respectively), were determined from two sets of recombinant cosmids. Among the 215 coding DNA sequences (CDSs) predicted in the TIRs of strain DSM40697, 65 are absent in the TIRs of strain ATCC23877. Reciprocally, 45 of the 194 predicted CDSs are specific to the ATCC23877 strain. The strain-specific CDSs are located mainly at the terminal end of the TIRs. Indeed, although TIRs appear almost identical over 150 kb (99% nucleotide identity), large regions of DNA of 60 kb (DSM40697) and 48 kb (ATCC23877), mostly spanning the ends of the chromosome, are strain specific. These regions are rich in plasmid-associated genes, including genes encoding putative conjugal transfer functions. The strain-specific regions also share a G+C content (68%) lower than that of the rest of the genome (from 71% to 73%), a percentage that is more typical of Streptomyces plasmids and mobile elements. These data suggest that exchanges of replicon extremities have occurred, thereby contributing to the terminal variability observed at the intraspecific level. In addition, the terminal regions include many mobile genetic element-related genes, pseudogenes, and genes related to adaptation. The results give insight into the mechanisms of evolution of the TIRs: integration of new information and/or loss of DNA fragments and subsequent homogenization of the two chromosomal extremities

Fiches descriptives des habitats marins benthiques de la Manche, de la Mer du Nord et de l’Atlantique

Ce catalogue présente l’ensemble des fiches descriptives des 108 unités de niveau 2 de la troisième version de la typologie NatHab-Atl (habitats marins benthiques de la Manche, de la Mer du Nord et de l’Atlantique), pour servir d’outil d’aide à l’identification et la conservation des habitats.Les habitats ont été décrits sur la base des descriptions existantes dans d’autres typologies complétées par les connaissances disponibles.Ce travail a permis de mettre à jour la typologie en modifiant le libellé de 10 unités pour clarifier leur contenu ou suivre les évolutions taxonomiques de leurs espèces caractéristiques, en supprimant une unité de niveau 3 et déplaçant les unités de niveau 4 qu’elle contenait.Ce travail a également permis d’identifier que le statut de présence en France de 22 unités était à confirmer.Toutes les fiches descriptives ainsi que des photos illustratives supplémentaires sont disponibles en ligne sur les pages habitats de l’INPN

Le REBENT-II Bretagne. Surveillance du Benthos du littoral breton. Années 2015-2016.

Ce « Rapport final » dresse le bilan des données REBENT acquises en 2015 et 201