Bacterial infections remain a major threat to human health. A better understanding about the fundamental mechanisms used by pathogenic bacteria to infect their host is necessary to identify novel targets for therapeutic intervention. The project presented here aims to further elucidate the complex interaction of intracellular bacterial pathogens with their host on the protein and posttranslational level. This will be achieved by analyzing key processes of bacterial cellular infection through innovative mass spectrometry-based proteome analyses which will provide unprecedented insight into the mechanisms of i) bacterial protein secretion ii) ubiquitin-like protein modification and iii) antigen presentation. Studies will be performed primarily on infection models with Listeria monocytogenes and Salmonella enterica, two major types of foodborne model pathogens causing human disease.