The bacterial cell envelope is one of the best targets for antimicrobial development. It is this envelope that harbours the instruments of microbial warfare, preventing its formation will therefore stop infection. This proposal focuses on one aspect of envelope formation, the movement of lipids between the membranes of the double membrane cell envelope. Until recently how lipids were transported between the membranes remained unknown, however, the Mla pathway, has been identified and provides the first evidence of a lipid transport pathway in gram-negative bacteria. However, how this pathway functions remains elusive. The aim of this proposal is to tackle these issues. Neutron reflectometry provides the ideal tool for monitoring the movement of lipids to and from the membrane and will provide vital information about how the Mla pathway functions.