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Identification et caractérisation de nouveaux ARN régulateurs chez Staphylococcus aureus : mise en évidence d’un regroupement de 5 transcrits

Abstract : Staphylococcus aureus is a human bacterial pathogen responsible for a wide spectrum of both hospital and community-acquired infections. The events involved in the switch between a commensal to an infectious state remain unclear. Nevertheless, they are correlated with a fine regulation of gene expression (including virulence factors), allowing the bacterium to efficiently adapts its growth and physiology to the local environment. Besides global transcriptional regulators, small RNAs (sRNA) have emerged as key players in the regulation of gene expression. Democratization of high-throughput RNA sequencing (RNA-seq) revealed that the identification of the whole sRNA content of S. aureus is not achieved yet. Therefore, the first aim of this thesis was to search for novel sRNAs in S. aureus Newman, a strain never used for such type of studies. Our investigation led to the discovery of 24 novel sRNAs. Among these, 7 belong to the core genome of S. aureus, confirming that the sRNA repertoire of this species, is not yet fully described.The characterization of these sRNAs demonstrated the presence of an unusual cluster composed of 5 sRNAs named Srn_9342 to Srn_9346. Study of Srn_9342, revealed that it is transcribed as two forms (Srn_9342short and Srn_9342long) with opposite gene expression profiles dependent on growth phase. The identification of the targets of these two forms by MAPS indicated that they would have different functions. Srn_9342short preferentially interacts with sRNAs described to play a role in virulence (RNAIII, SprD and RsaC). Therefore, we suggested that the short form would have a role as a sRNA sponge. Regarding the long form and according to the targets enriched by MAPS, this sRNA may contribute to the adaptation of the bacterium to the different stresses encountered during infection. Validation and study of these potential partners will help to better understand the role of Srn_9342s within bacterial physiology.
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Julie Bronsard. Identification et caractérisation de nouveaux ARN régulateurs chez Staphylococcus aureus : mise en évidence d’un regroupement de 5 transcrits. Biochimie, Biologie Moléculaire. Université Rennes 1, 2019. Français. ⟨NNT : 2019REN1B014⟩. ⟨tel-02957218⟩

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