Human body surfaces are colonized by highly complex and variable consortia of microorganisms, so called microbiota, which play essential roles for many human body functions. In fact, humans have more bacterial than body cells together constituting a ‘metaorganism’. Only a small minority of the bacterial colonizers can be pathogens but these bacteria are highly relevant because they are responsible for the vast majority of invasive, often fatal infections. Despite its importance the microbial ecology of human body surfaces has hardly been explored.
Staphylococcus aureus is a constituent of the nasal microbiota in 20-30% of the human population and also represents the most frequent cause of life-threatening invasive infections in the northern hemisphere. The individual predisposition to S. aureus colonization and the transition from commensal to pathogenic life-styles represent exciting examples of microbe-host coevolution and adaptation processes. We are studying the underlying principles of S. aureus nasal colonization, metabolic adaptation and fitness, and resistance to defensin-like antimicrobial peptides.