Iron sources for Haemophilus ducreyi

The ability of various haem- and non-haem-iron-containing compounds to support the growth of iron-limited cultures of Haemophilus ducreyi was assessed in a plate bioassay. Only haemin or the haem-containing proteins, bovine haemoglobin, human haemoglobin and bovine catalase, but not equine cytochrome C111, were capable of serving as the sole exogenous iron source. Complexes of haptoglobin-haemoglobin and haem-serum albumin retained the ability to function as iron substrates. In contrast, no growth was observed with FeCl3, human lactoferrin and human transferrin. Siderophore production was not detected with a universal chemical assay. Outer-membrane-protein profiles derived from iron-starved cultures revealed four iron-regulated polypeptides of 65, 50, 45.5 and 40.5 Kda. These results indicate that haem can supply the requisite iron for growth of H. ducreyi.