ABSTRACT
The enteropathogenic Yersinia enterocolitica strains have several systems for scavenging iron from their environment. We have studied the expression of the fyuA gene, which encodes the outer membrane receptor for the siderophore yersiniabactin (Ybt), and the hemR gene, which encodes the receptor for heme, using the reporter genes gfp (encoding green fluorescent protein) and luc (encoding firefly luciferase). To study gene expression in vitro as well as in vivo, we have constructed several translational reporter gene fusions to monitor simultaneously expression of fyuA andhemR or expression of one gene by agfp-luc tandem reporter. Results of the in vitro expression analysis (liquid media) indicated that fyuA and hemR are strongly derepressed under iron starvation conditions, resulting in strong fluorescence and/or luminescence at 27°C. In the in vivo BALB/C mouse infection model, tissue-specific expression of fyuA andhemR reporter fusions was observed. Surprisingly,fyuA and hemR reporter constructs were weakly expressed by yersiniae located in the liver and intestinal lumen, whereas strong expression was found for yersiniae in the peritoneal cavity and moderate expression was found in the spleen. Strikingly, yersiniae carrying fyuA orhemR reporter fusions exhibited threefold-stronger signals when grown in the peritoneal cavity of mice than those growing under iron derepression in vitro. This hyperexpression suggests that besides Fur derepression, additional activators may be involved in the enhanced expression of fyuA and hemRunder peritoneal growth conditions. Differential expression of thefyuA and hemR reporter fusions could not be observed, suggesting similar regulation of fyuA andhemR in the mouse infection model.
Neuromedin B and Gastrin-Releasing Peptide Excite Arcuate Nucleus Neuropeptide Y Neurons in a Novel Transgenic Mouse Expressing Strong Renilla Green Fluorescent Protein in NPY Neurons
