Entwicklung und Anwendung von Massenspektrometrie basierten Methoden zur Identifizierung und Quantifizierung von Zelloberflächen assoziierten Proteinen des humanpathogenen Bakteriums Staphylococcus aureus MRSA Staphylococcus aureus Tandem Massenspektrometrie Massenspektrometrie HPLC MS Elektronensprayionisations Massenspektrometrie LC MS The human pathogenic bacterium Staphylococcus aureus causes a wide variety of in part life threatening diseases such as skin infections (furunculosis) pneumonia osteomyelitis endocarditis and sepsis. Thereby S. aureus belongs to the most prevalent pathogenic agents of nosocomial infections. Antibiotic treatment becomes more challenging because of an increasing frequency of multiple antibiotic resistances as S. aureus is capable of adapting to rapidly changing environmental conditions. The interaction of this pathogenic bacterium with its environment and its host is specifically based on the protein set presented on the surface of the bacterial cell. S. aureus expresses an arsenal of cell surface associated virulence factors leading to colonization and infection of human tissue. The aim of this work was the development and implementation of mass spectrometry based approaches for identification and quantification of cell surface associated proteins of the human pathogenic bacterium Staphylococcus aureus. Thereby access to 77% of all known cell surface associated proteins and two thirds of all external exposed membrane anchored lipoproteins was enabled by the gel free and GeLC MS MS based methods named biotinylation and trypsin shaving. Biotinylation implies the labeling of cell surface associated proteins of intact staphylococcal cells by a membrane impermeable biotinylation reagent and subsequent enrichment by affinity chromatography. In contrast trypsin shaving is the proteolytical digestion of all cell surface exposed protein domains. In addition a relative quantification of the surface associated proteins by labeling of the proteins with stable isotopes the 14N 15N metabolic labeling was enabled for the first time ...