EFFECT OF PROTOPORPHYRIN-IX LIMITATION ON PORPHYROMONAS-GINGIVALIS

Porphyromonas gingivalis has been shown to require hemin or hemoglobin for in vitro growth. We have previously shown that protoporphyrin IX and inorganic iron can replace the hemin requirement, suggesting that the hemin requirement of this microorganism is actually a porphyrin re quirement, We examined the effect of protoporphyrin IX limitation to P . gingivalis strain A7A1-28 in the presence of sufficient iron on grow th characteristics, proteolytic enzyme production, virulence in a mous e abscess model, and expression of membrane proteins, Bacterial cells were grown in medium varying between 0 to 5 mu M protoporphyrin IX, Pr otoporphyrin IX levels <0.25 mu M reduced growth by at least 50%. Prot oporphyrin IX availability did not affect proteolytic enzyme productio n or virulence in a mouse abscess model, Sodium dodecyl sulfate-polyac rylamide gel electrophoresis of membrane preparations demonstrated tha t protoporphyrin IX limitation induced the expression of new proteins at 42, 34, 30, 29, and 18 kDa and suppressed the production of protein s at 47, 27, 17, and 15 kDa, These studies suggest that in vivo protop orphyrin availability may modulate membrane protein expression and in turn affect host immune responses against P. gingivalis.