The periodontal pathogen Porphyromonas gingivalis harnesses the chemistry of the μ-oxo bishaem of iron protoporphyrin IX to protect against hydrogen peroxide

Abstract

The major haem component in the black pigment of Porphyromonas gingivalis is the μ-oxo bishaem of iron protoporphyrin IX and formation and cell-surface binding of this haem species is proposed as an extracellular buffer against reactive oxidants [Smalley, J.W. et al. (1998) Biochem. J. 331, 681–685]. P. gingivalis cells grown in the presence of the μ-oxo bishaem were protected against H 2O 2 compared to control cells grown without it. When added to the growth medium, soluble μ-oxo bishaem inactivated H 2O 2 and supported cell growth. Cells carrying a surface layer of μ-oxo bishaem were less susceptible to peroxidation by H 2O 2. Cell-surface haems were slowly destroyed during reaction with H 2O 2. Binding of μ-oxo bishaem by P. gingivalis may aid survival during neutrophil attack through inactivation of hydrogen peroxide.