Endogenously produced HO is intimately involved in iron metabolism in .

Heme degradation provides pathogens with growth essential iron, leveraging on the host heme reservoir. Bacteria typically import and degrade heme enzymatically, and here, we demonstrated a significant deviation from this dogma. We found that liberates iron from met-hemoglobin extracellularly, in a hydrogen peroxide (HO)- and cell-dependent manner; this activity serves as a major iron acquisition mechanism for . Inhabiting oxygen-rich environments is a major part of pneumococcal biology, and hence, HO-mediated heme degradation likely supplies iron during infection. Moreover, HO reaction with ferrous hemoglobin but not with met-hemoglobin is known to result in heme breakdown. Therefore, the ability of pneumococci to degrade heme from met-hemoglobin is a new paradigm. Lastly, this study will inform other research as it demonstrates that extracellular degradation must be considered in the interpretations of experiments in which HO-producing bacteria are given heme or hemoproteins as an iron source.