SdiA, an N-Acylhomoserine Lactone Receptor, Becomes Active during the Transit of Salmonella enterica through the Gastrointestinal Tract of Turtles

encode a LuxR-type AHL receptor, SdiA, they cannot synthesize AHLs. In vitro, it is known that SdiA can detect AHLs produced by other bacterial species..We conclude that the normal gastrointestinal microbiota of most animal species do not produce AHLs of the correct type, in an appropriate location, or in sufficient quantities to activate SdiA. However, the results obtained with turtles represent the first demonstration of SdiA activity in animals

SdiA sensing of acyl-homoserine lactones by enterohemorrhagic E. coli (EHEC) serotype O157:H7 in the bovine rumen

Chemical communication mediates signaling between cells. Bacteria also engage in chemical signaling, termed quorum sensing (QS), to coordinate population-wide behavior. The bacterial pathogen enterohemorrhagic E. coli (EHEC), responsible for outbreaks of bloody diarrhea worldwide, exploits QS to promote expression of virulence factors in humans. Although EHEC is a human pathogen, it is a member of the gastrointestinal (GI) flora in cattle, the main reservoir for this bacterium. EHEC cattle colonization requires SdiA, a QS transcription factor that uses acyl-homoserine lactones (AHLs), for proper folding and function. EHEC harbors SdiA, but does not produce AHLs, consequently having to sense AHLs produced by other bacterial species. We recently showed that SdiA is necessary for efficient EHEC passage through the bovine GI tract, and show that AHLs are prominent within cattle rumen, but absent from the other sections of the GI tract. EHEC utilizes the locus of enterocyte effacement (LEE) to colonize the recto-anal junction of cattle, and the glutamate decarboxylase (gad) system to colonize cows. Transcription of the LEE genes is decreased by rumen AHLs through SdiA, while transcription of the gad acid resistant system is increased. It would be expensive for EHEC to express the LEE genes in the rumen where they are not necessary. However, in preparation for the acidic distal stomachs the EHEC gad is activated in the rumen. Hence AHL signaling through SdiA aids EHEC in gauging these environments, and modulates gene expression towards adaptation to a commensal life-style in cattle.1 Inasmuch as EHEC is largely prevalent in cattle herds, interference with SdiA-mediated QS inhibition of cattle colonization could be an attractive approach to diminish contamination of food products due to cattle shedding of this pathogen

Mixed High-Speed, Conventional and Metro Central Rail Stations as Places to Work: The Case Study of Naples

International audienceToday, rail stations tend to be considered as nodes but also as places within an area. In this respect, different types of shops and services can be present in rail stations. High Speed Rail services tend to increase the importance of the train station as a place. Our aim is to show that in some cases, some firms extend the role of the station as a place by using high speed train stations to provide temporary offices inside them. Thus the role of the station as a place is transformed in a place to work for mobile workers, a kind of third-place. This is the case of Regus, which is the world's leading provider of flexible workspaces all over the world, supporting over 1 million customers everyday. The objective of this contribution is to identify the characteristics of the clients of the temporary Regus offices in the Naples HSR station and the role of HSR in this context. For this purpose, a recent survey has been employed, interviewing clients using Regus offices. Data concerning the clients have been collected, such as socio-economic characteristics, transport mode chosen to reach Naples and the Regus services used