The anti-bacterial iron-restriction defence mechanisms of egg white; the potential role of three lipocalin-like proteins in resistance against Salmonella

Salmonella enterica serovar Enteritidis (SE) is the most frequently-detected Salmonella in foodborne outbreaks in the European Union. Among such outbreaks, egg and egg products were identified as the most common vehicles of infection. Possibly, the major antibacterial property of egg white is iron restriction, which results from the presence of the iron-binding protein, ovotransferrin. To circumvent iron restriction, SE synthesise catecholate siderophores (i.e. enterobactin and salmochelin) that can chelate iron from host iron-binding proteins. Here, we highlight the role of lipocalin-like proteins found in egg white that could enhance egg-white iron restriction through sequestration of certain siderophores, including enterobactin. Indeed, it is now apparent that the egg-white lipocalin, Ex-FABP, can inhibit bacterial growth via its siderophore-binding capacity in vitro. However, it remains unclear whether ex-FABP performs such a function in egg white or during bird infection. Regarding the two other lipocalins of egg white (Cal-γ and α-1-glycoprotein), there is currently no evidence to indicate that they sequester siderophores

Characterization of the Erwinia chrysanthemi osmoprotectant transporter gene ousA

International audienceGrowth of Erwinia chrysanthemi in media of elevated osmolarity can be achieved by the uptake and accumulation of various osmoprotectants. This study deals with the cloning and sequencing of the ousA gene-encoded osmoprotectant uptake system A from E. chrysanthemi 3937. OusA belongs to the superfamily of solute ion cotransporters. This osmotically inducible system allows the uptake of glycine betaine, proline, ectoine, and pipecolic acid and presents strong similarities in nucleotide sequence and protein function with the proline/betaine porter of Escherichia coli encoded by proP. The control of ousA expression is clearly different from that of proP. It is induced by osmotic strength and repressed by osmoprotectants. Its expression in E. coli is controlled by H-NS and is rpoS dependent in the exponential phase but unaffected by the stationary phase

Synchrotron Radiation µCT : A Reference Tool for the Characterization of Bone Samples

International audienceTomographic techniques are attractive for the analysis of bone micro-architecture since they are non-destructive and may provide images of bone samples in three dimensions. Currently, two modalities are available: x-ray µCT (Micro-Computerized Tomography) and MRI (Magnetic Resonance Imaging). Due to the typical dimensions of trabeculae, specific µCT or MRI devices had to be developed.1,2Whereas both types of devices may deliver 3D images of bone architecture, the characteristics of these images differ 3D images of bone architecture, the characteristics of these images differ meaningfully. First, the parameter that is imaged is related to the corresponding phenomenon, either the x-rays absorption coefficient in /lCT, or the protons’ magnetization in MRI. Second, the two modalities do not offer the same spatial resolution and image quality. For in vivo imaging, an inslice spatial resolution around 100-150µlm. with a generally larger slice thickness, is typically achievable with both modalities.3, 4However, the use of x-ray µlCT is restricted to peripheral sites, such as the forearm, and this typical spatial resolution might not be significantly improved considering the problem of dose delivery. For in vitro imaging, much higher spatial resolutions are attainable at this time. In µlMRI (Micro-MRI), images of bone samples with isotropic spatial resolution of 50 µlm have been reported.5In x-ray µlCT, images with voxel sizes up to 28 µlm are available.6, 7Furthermore, the use of x-rays generated from synchrotron sources permits a spatial resolution of 1µlm