During infection, the host immune system interacts with the bacterial cell surface, a complex structure made of peptidoglycan, wall teichoic acids, lipoteichoic acids, capsule polysaccharide and peptidoglycan-attached proteins. A lot is known about the metabolic pathways for the synthesis of each individual cell surface component. Almost nothing is known about the coordination between the synthesis of the peptidoglycan, the major structural component of the cell surface and the main inflammatory component of gram-positive bacteria, and the synthesis of the other molecules present at the surface. However, this coordination is essential for the construction of a surface capable not only of performing its biological functions in cell protection and morphology, but also of masking its inflammatory components for evasion from host recognition.Using the clinical pathogen Staphylococcus aureus as a model organism, we propose to investigate the temporal and spatial regulation of the enzymes responsible for the synthesis of the cell surface components, as well as their dependence on the underlying divisome.We will (i) use state-of –the art fluorescence microscopy to localize fluorescent derivatives of enzymes required for cell surface synthesis; (ii) use libraries of antibiotics, of antisense RNA expression plasmids, and of transposon mutants to identify the order of assembly and requirements for the localization of cell surface synthesis enzymes; (iii) identify the exact metabolic compound/protein/geometric cue responsible for the localization of key enzymes; (iv) determine if cells with impaired surface synthesis due to protein delocalization are more susceptible to host recognition and therefore less capable of causing infections.This project will result in the identification of new mechanisms of protein localization, a fundamental question in cell biology, and in a better understanding of the assembly of the bacterial cell surface of successful bacterial pathogens