UTILIZATION OF HEME FROM THE HAPTOGLOBIN-HEMOGLOBIN COMPLEX BY BACTEROIDES-FRAGILIS

Possession of specialized iron acquisition systems is a prerequisite f or the survival of pathogenic bacteria in their host. The purpose of t his study was to determine whether Bacteroides fragilis, a clinically important Gram-negative anaerobic bacterium, possesses a specific haem -uptake system. Growth studies indicated that this microorganism can u tilize haem from either haemoglobin or haptoglobin-haemoglobin as its sole source of iron. Iron-repressible haem-binding protein complexes ( HBP complexes), involved in the uptake of haem from haptoglobin-haemog lobin were detected by means of lithium dodecyl sulfate polyacrylamide gel electrophoresis (LDS-PAGE). Four polypeptides of approximately 60 , 58, 49 and 35 kDa, which are part of these HBP complexes, were ident ified as haem-binding proteins. A 44 kDa iron-repressible outer-membra ne protein is needed for a functional HBP complex, but the exact role of this protein in the uptake of haem is still unknown.