Bartonella henselae causes cat-scratch disease and bacillary angiomatosis peliosis. The bacteria reside in erythrocytes of asymptomatic cats, which represent the natural reservoir for this pathogen. B. henselae is usually grown on blood-enriched media. Growth experiments on Brucella medium without blood demonstrated that heme compounds are essential for the growth of B. henselae and can completely substitute the addition of blood components. The heme precursor protoporphyrin IX alone, or in combination with FeCl(2) or FeCl(3), as well as transferrin or lactoferrin did not support growth, indicating that B. henselae cannot synthesize heme itself. Hemin supported growth even when free iron was chelated, indicating that hemin is also used as an iron source. Binding assays showed that hemin starvation increased the binding capacity of B. henselae for hemin, providing evidence that the bacteria carry a specific hemin uptake system, which might be regulated by hemin.