Iron Acquisition from Heme and Hemoglobin by a Serratia marcescens Extracellular Protein

Several pathogenic bacteria are able to use heme and hemoproteins as iron sources independent of siderophore production by mechanisms involving outer membrane heme-binding proteins and heme transport systems. Here we show that Serratia marcescens has such a property and we identify an extracellular heme-binding protein, HasA (for heme acquisition system), allowing the release of heme from hemoglobin. This protein is secreted by S. marcescens under conditions of iron depletion and is essential for heme acquisition.