Salmonella Strains Isolated from Galápagos Iguanas Show Spatial Structuring of Serovar and Genomic Diversity

It is thought that dispersal limitation primarily structures host-associated bacterial populations because host distributions inherently limit transmission opportunities. However, enteric bacteria may disperse great distances during food-borne outbreaks. It is unclear if such rapid long-distance dispersal events happen regularly in natural systems or if these events represent an anthropogenic exception. We characterized Salmonella enterica isolates from the feces of free-living Galápagos land and marine iguanas from five sites on four islands using serotyping and genomic fingerprinting. Each site hosted unique and nearly exclusive serovar assemblages. Genomic fingerprint analysis offered a more complex model of S. enterica biogeography, with evidence of both unique strain pools and of spatial population structuring along a geographic gradient. These findings suggest that even relatively generalist enteric bacteria may be strongly dispersal limited in a natural system with strong barriers, such as oceanic divides. Yet, these differing results seen on two typing methods also suggests that genomic variation is less dispersal limited, allowing for different ecological processes to shape biogeographical patterns of the core and flexible portions of this bacterial species' genome

Villes intelligentes et inégalités territoriales : quelles actions menées pour lutter contre les inégalités ?

International audienc

Recursive Least-Squares in Feature Space for System Identification

International audienc

Study on sulfur deactivation of catalysts for DMDS oxidation

Abstract In the present research, an industrially aged Pt/Al₂O₃ catalyst was used as a basis for the study on the sulfur deactivation and the development of more resistant catalytic materials. The catalytic activities of both industrially and laboratory-aged materials in DMDS oxidation were studied in addition to characterization by XRD, XPS, FESEM, TEM and N₂ adsorption. The industrial ageing induced a phase change from γ-Al₂O₃ towards θ-Al₂O₃, formation of aluminum sulfates and an increase in Pt particle size as well as a change in the oxidation state of Pt to a higher state. These changes caused an increase of 30 °C in the light-off temperature for DMDS oxidation. Accelerated ageing in the presence of SO₂ and H₂O vapor at 400 °C for 5 h decreased the activity of the Pt/Al₂O₃ at the same level than for the industrially aged catalyst even though smaller sulfur content and no sintering of γ-Al₂O₃ were observed. Pt sintering (10–20 nm) in both cases was observed. The XPS results confirmed the formation of new sulfate phases and the interaction between sulfur and the active phase as well as the support of the catalyst undergone accelerated ageing. After the accelerated ageing of copper-based catalysts, the 0.3Pt10Cu/Al₂O₃ǀ0.8SiO₂ǀ0.2 catalyst showed an interesting resistance towards sulfur deactivation, as it was expected