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Séminaire de Beata BASTA

par Webmestre - publié le

Iron acquisition pathway expression in P. aeruginosa during cells infection and in
biofilm cultures

Vendredi 8 Avril — 11 h — P5 salle 172

Dr Beata BASTA, UMR 7242 Université de Strasbourg-CNRS

Subject : Pseudomonas aeruginosa, is an opportunistic human pathogen, strongly involved in severe and often fatal infections in patients with cystic fibrosis. Like almost all living organism, P. aeruginosa has a strong iron requirement, and it fulfills its iron needs by producing large amounts of two chemically unrelated siderophores, pyoverdin (PVD) and pyochelin (PCH). These two compounds function as powerful iron chelators, solubilizing iron in the environment of the bacteria and afterwards transporting it into the bacterial cells. In our group, we aim to develop “Trojan horse” prodrugs having as target these ferri-siderophore uptake pathways to fight Pseudomonas aeruginosa infections. In order to develop such strategy, we need to have a good knowledge of these iron uptake pathways. Here, we address the comparative importance of both, PVD and PCH iron acquisition pathways in two different growth conditions : biofilms and in model of cellular infections.

Methods : The effect of Pseudomonas aeruginosa and its siderophore-producing mutants on the growth and viability of human lung adenocarcinoma-derived epithelial cells was determined by MTT assay. Expression of PVD and PCH biosynthesis and iron uptake in Pseudomonas aeruginosa during epithelial cells infection and biofilm creation were assessed by confocal microscopy using P. aeruginosa cells expressing fluorescent tagged proteins of both the PVD and the PCH pathways.

Results : We have found important difference in the virulence of the bacteria, able to produce different siderophores in our infections model. Additionally, microscopy experiments have further revealed high level of expression of both PVD and PCH pathways during infection. Within the biofilm culture, we saw as well expression of both pathways, but only in the cells located at the base of the biofilm. Much less expression was observed in the mushroom structures.

Discussion and Conclusion : We succeeded in showing experimentally the impact of siderophore production on P. aeruginosa infections. For the first time, we were able to visualize expression of proteins involved in both PVD and PCH pathways during the infection process, demonstrating that these pathways are expressed in this growth conditions and therefore can be used as target for the design and development of “Trojan horse” prodrugs. Concerning biofilm cultures, our strategy also allowed us for the first time to visualize were in the biofilm are expressed PVD and PCH pathways.