Défense de thèse de doctorat en sciences biologiques : "Bacteroidetes"

Investigation of the surface lipoprotein export machinery of Bacteroidetes

Jury

Wilbert BITTER (VU University Amsterdam), Jean-François COLLET (UCL), Xavier DE BOLLE, président (UNamur), Johan WOUTERS (UNamur), Guy CORNELIS, promoteur (UNamur)

Résumé

Gram-negative bacteria of the phylum Bacteroidetes are important mammal commensals and pathogens. Understanding their biology is therefore a key question in particular for human health. A main feature of these bacteria is the presence of abundant lipoproteins at their surface, often clustered into multi-protein membrane complexes that are crucial for nutrient acquisition. To date, little is known on how these complexes assemble and in particular on how lipoproteins reach the bacterial surface.

Here, using in silico analyses and site directed mutagenesis, we show that Bacteroidetes surface lipoproteins share an N-terminal signal that drives surface localization. The position and the overall negative charge of the lipoprotein export signal (LES) are crucial for its role. We also focused at identifying the underlying lipoprotein transport machinery. Using in silico predictions and pulldown experiments, we identified several essential proteins involved in outer membrane biogenesis of Bacteroidetes. Their precise function and involvement in lipoprotein export is currently under investigation.

Overall, our findings provide the first evidence that Bacteroidetes are endowed with a new bacterial lipoprotein export pathway that flips lipoproteins across the outer membrane.

La défense est publique

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