Use of hemoglobin as an iron source by Bacillus cereus

The hemoglobin binding activity of Bacillus cereus cells was measured with fluoresceinisothiocyanate (FITC)-conjugated hemoglobin using flow cytometry. Growth of B. cereus was markedly inhibited by the addition of apo-transferrin. B. cereus could not use transferrin-bound iron as an iron source in serum. The growth inhibition was reversed by the addition of a FeCl3 solution, erythrocytes or hemoglobin. B. cereus released hemolysin; these findings suggested that the hemoglobin released from erythrocytes by B. cereus hemolysin binds to B. cereus and is thus used as an iron source.