Friday, 23th September, 2022
Luis Orenday Tapia will present their research on study of Mechanisms of biogenesis and maintenance of the outer membrane of Gram-negative bacteria.
Gram-negative bacteria encompass many multidrug resistant pathogens. Their multilayered envelope is formed by an inner membrane (IM), an outer membrane (OM), and a separating periplasm containing the peptidoglycan (PG). The OM forms a semipermeable barrier that prevents the entry of numerous chemicals. Lipoproteins and integral OM proteins (OMPs) are crucial components of the OM that exchange nutrients, excrete toxic molecules and interact with the environment. The OM contains lipopolysaccharide (LPS) in the external leaflet and phospholipids in the internal one. All OM components are synthesized in the cytosol or at the IM and are delivered to the OM by specific transport pathways. Among these, the β-barrel assembly machinery (BAM) complex folds and inserts OMPs into the OM. The assembly of some OMPs requires the poorly understood activity of the translocation and assembly module (TAM). The accumulation of unfolded OMPs in the periplasm triggers activation of the σE-mediated envelope stress response. σE regulates a number of genes enhancing the levels of BAM subunits. Whereas many envelope biogenesis pathways have been described in the last decades, little is known about how these processes are coordinated during the life cycle of the cell.
This PhD project aimed at studying the regulation of BAM by determining all BAM interactions in the envelope of the enterobacterium Escherichia coli. We setup a quantitative proteomic approach to analyze the BAM complex purified upon mild-solubilization of the cell envelope. The identified BAM putative interactors include two key envelope proteins, the division and OM-stress associated lipoprotein DolP/YraP and the IM-anchored transporter protein TamB. During my PhD defense on the 23rd of september 2022, I will present my results on how the interplay of BAM with both DolP and TamB contributes to form and preserve an effective semipermeable barrier that protects bacteria from stress and noxious molecules including antibiotics.
Thesis defense will be preceded by 2 seminars of 30 minutes each:
– Peter van Ulsen (Vrije Universiteit, Amsterdam) : “Autotransporter Hbp as model, vehicle and target”
– Alessandra Polissi (Università di Milano) : “Peptidoglycan remodeling as a strategy to survive outer membrane stress in Escherichia coli “