Probing the role of outer membrane transport processes in host-­pathogen interactions using computational and single-­molecule biophysical approaches. (360G-Wellcome-109317_Z_15_A)

The outer membrane (OM) of Gram-negative bacteria is a significant protective barrier. It is composed of an inner leaflet of phospholipids and an outer of lipopolysaccharide (LPS) with OM proteins (OMPs) that span the membrane. Recently OMPs have been shown to be inserted at discrete and non-uniform locations across the membrane, where they remain due to restricted lateral diffusion. These ‘islands’ are pushed to the poles by cell growth, with new material inserted at mid-cell. OM turnover during bacterial growth may have a role in immune system evasion. One key mechanism regulating human immune responses is the assembly of complement components on the OM nucleated by immunoglobulin binding. This process can lead to lysis of bacteria through insertion of pore complexes in the OM. Complex formation depends on localised clustering of antibodies, which is constrained by the location and molecular diffusion of antigens in the OM. In this project we will use computational and single-cell biophysical techniques to test our hypothesis that spatial confinement of LPS and OMPs near their insertion sites influences activation of the antibody-mediated complement pathway. We will test our hypothesis in Escherichia coli and Salmonella typhimurium, where immune evasion has a key role in pathogenesis.