Staphylococcus lugdunensis IsdG liberates iron from host heme

Staphylococcus lugdunensis is often found as part of the normal flora of human skin but has the potential to cause serious infections even in healthy individuals. It remains unclear what factors enable S. lugdunensis to transition from a skin commensal to an invasive pathogen. Analysis of the complete genome reveals a putative iron-regulated surface determinant (Isd) system encoded within S. lugdunensis. In other bacteria, the Isd system permits the utilization of host heme as a source of nutrient iron to facilitate bacterial growth during infection. In this study, we establish that S. lugdunensis expresses an iron-regulated IsdG-family heme oxygenase that binds and degrades heme. Heme degradation by IsdG results in the release of free iron and the production of the chromophore staphylobilin. IsdG-mediated heme catabolism enables the use of heme as a sole source of iron, establishing IsdG as a pathophysiologically relevant heme oxygenase in S. lugdunensis. Together these findings offer insight into how S. lugdunensis fulfills its nutritional requirements while invading host tissues and establish the S. lugdunensis Isd system as being involved in heme-iron utilization.