Comparison of iron uptake of four Helicobacter species (Helicobacter pylori, Helicobacter felis, Helicobacter acinonyx, and Helicobacter mustelae), associated with various degrees of gastritis in their respective host, with five other species which colonize the intestinal tract of various animals (Helicobacter fennelliae, Helicobacter cinaedi, Helicobacter muridarum, Helicobacter bilis, and Helicobacter hepaticus), demonstrated that the iron acquisition system differed according to the ecological niche of the organism. Gastric Helicobacter, except for H. pylori, which used iron from human lactoferrin, were nonsiderophore-producing organisms and were only able to obtain iron from heme and hemoglobin. Nongastric Helicobacter produced siderophores and were able to use for growth a wide range of iron sources (bovine and human lactoferrin and transferrin, heme, hemoglobin).