The periodontal pathogen Porphyromonas gingivalis harnesses the chemistry of the mu-oxo bishaem of iron protoporphyrin IX to protect against hydrogenperoxide

The major haem component in the black pigment of Porphyromonas gingivalis i s the mu-oxo bishaem of iron protoporphyrin IX and formation and cell-surfa ce binding of this haem species is proposed as an extracellular buffer agai nst reactive oxidants [Smalley, J.W. et al. (1998) Biochem. J. 331, 681-685 ], P. gingivalis cells grown in the presence of the mu-oxo bishaem were pro tected against H2O2 compared to control cells grown without it. When added to the growth medium, soluble mu-oxo bishaem inactivated H2O2 and supported cell growth, Cells carrying a surface layer of mu-oxo bishaem were less su sceptible to peroxidation by H2O2. Cell-surface haems were slowly destroyed during reaction with H2O2 Binding of mu-oxo bishaem by P. gingivalis may a id survival during neutrophil attack through inactivation of hydrogen perox ide, (C) 2000 Federation of European Microbiological Societies. Published b y Elsevier Science B.V. All rights reserved.