Niche competition by human-associated Staphylococcus species

Bernhard Krismer
University of Tübingen, Tübingen, Allemagne

The microbiomes on human body surfaces affect health in multiple ways since they include not only commensal or mutualistic bacteria but also potentially pathogenic bacteria. Staphylococci belong to the most prominent members of the human microbiome, predominantly colonizing the skin and nares. Besides the most abundant species, Staphylococcus epidermidis, the nose is frequently also colonized by the potentially pathogenic Staphylococcus aureus. Competition for epithelial attachment sites or limited nutrients, different susceptibilities to host defense molecules and the production of antimicrobial molecules may determine whether different nasal bacteria outcompete each other. We have recently identified lugdunin, produced by nasal Staphylococcus lugdunensis, which is able to eradicate S. aureus. Interestingly, at the same time this species is dependent on the acquisition of xenosiderophores. But the armory of nasal bacterial isolates includes many more still unidentified compounds, which might play an important role in niche competition. We have now identified epifadin, a highly unstable but broad-acting molecule produced by an NRPS/PKS biosynthetic gene cluster, in various S. epidermidis isolates. Constitutive production but short half-live might represent a special strategy in bacterial warfare to reduce unintended collateral damage of supporting co-inhabitants. Unexpectedly, also a well-known molecule from fungi and soil bacteria might play an important role in bacterial rivalry on the human host.