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Contrôle de l'homéostasie de fer au cours du cycle infectieux d'Erwinia chrysanthemi 3937

Abstract : The pathogenic enterobacterium Erwinia chrysanthemi 3937 is able to cause soft-rot disease on a large set of plants. In the host, bacteria disseminate extracellularly and encounter an oxidative environment with low iron availability. Under these conditions, a tight control of the intracellular iron pool is important since excess of iron can exacerbate oxidative stress by generating the highly toxic radical OH° through the Fenton's reaction. Iron homeostasis involves ferritins which sequester iron under a non reactive state. These iron stores can be used to enhance bacterial growth when external iron supplies are restricted. The genome of E. chrysanthemi 3937 presents a hundred of genes involved in iron metabolism including four loci that could be devoted to iron storage : the ftnA gene encoding an eukaryotic type haem-free ferritin, the bfr gene coding for a haem-containing bacterioferritin and, the dps1 and dps2 genes encoding two Dps proteins (DNA-binding proteins from starved cells). Our work is aimed at elucidating the role of these proteins in iron homeostasis and pathogenicity of E. chrysanthemi 3937. According to their differential role in iron storage, the ftnA, bfr and dps1 genes appeared to be controlled differently by iron and Fur (ferric uptake regulator). Only the iron and Fur-induction of ftnA gene is dependent of the small antisens RyhB RNA. Moreover, the dps1 and bfr genes are regulated by additional effectors including the σS transcription factor. Disruption of the ftnA, bfr and dps1 genes showed that FtnA is the main cellular component involved in iron storage. However, these ferritins are not only involved in iron storage : FtnA contributes to oxidative stress resistance and Dps1 could be implicated in hydrogen peroxide detoxication through its ferroxidase center. The implication of these proteins to bacterial virulence is also discussed.
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https://tel.archives-ouvertes.fr/tel-00679480
Contributor : Aida Boughammoura <>
Submitted on : Thursday, March 15, 2012 - 4:48:02 PM
Last modification on : Wednesday, December 9, 2020 - 3:10:41 PM
Long-term archiving on: : Wednesday, December 14, 2016 - 12:48:46 PM

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  • HAL Id : tel-00679480, version 1
  • PRODINRA : 245379

Citation

Aida Boughammoura. Contrôle de l'homéostasie de fer au cours du cycle infectieux d'Erwinia chrysanthemi 3937. Microbiologie et Parasitologie. Université Paris Sud - Paris XI, 2007. Français. ⟨tel-00679480⟩

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