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Les transporteurs de peptides de Staphylococcus aureus

Aurélia Hiron
Abstract : In bacteria, peptides are internalized by dedicated transporters and have been shown to play key roles in nutrition, signalling and virulence. Very few information is available on peptide transporters in S. aureus, a major pathogenic bacteria. Then, the systematic analysis of these systems was the main objective of my project. Systematic in silico analysis of 12 different S. aureus genomes revealed the existence of (i) four opp operons (opp1, opp2, opp3 and opp4), (ii) one orphan opp5A gene encoding a putative peptide-binding protein and (iii) a dtpT gene encoding a di- tripeptide permease. With the exception of opp4, all systems were present in each S. aureus strain. Within a single strain, the different opp operons displayed little sequence similarity and distinct genetic organization. To identify both the role and the specificity of these transporters, defined deletion mutants in one or several peptide transporters were constructed. Results showed that among these systems, only Opp3 and DtpT are involved in nitrogen nutrition. They supply the cell with peptides from 3 to 8 amino acids of length and di- tripeptides, respectively. Their function is required for to the optimal growth of the bacteria in milk. In this medium, in addition to provide peptides as nutrients, Opp3 participates to the regulation of two exocellular proteinase-encoding genes, namely ssp and aur. The precise mechanism by which this transporter exerts this latter function remains to be elucidated. Some Gram-positive bacteria use for cell-cell communication short secreted peptides (pheromones), which are imported back by Opp. To evaluate a possible pheromone production by S. aureus, the peptide content of the chemically defined medium was analyzed after microbial growth by mass spectrometry. Results were submitted to a data bank specially designed for short genes detection. This approach made it possible to evidence for the production of 5 uncharacterized peptides. Their biological functions have to be investigated. Finally, as peptide-binding and nickel-binding proteins are not distinguished on the basis of their sequence comparison, we evaluated the ability of one (or several) of the S. aureus Opp systems to transport nickel. The involvement of Opp2 and Opp5A in this function was demonstrated. Our results evidenced for the nutritional role of Opp3 and DtpT. As Opp2 and Opp5A are involved in nickel transport, only the roles of Opp1 and Opp4 remain to be characterized.
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Submitted on : Thursday, June 5, 2008 - 8:00:00 AM
Last modification on : Thursday, June 5, 2008 - 8:00:00 AM
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Aurélia Hiron. Les transporteurs de peptides de Staphylococcus aureus. Life Sciences [q-bio]. AgroParisTech, 2007. English. ⟨pastel-00003802⟩

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