Temperature elevation regulates iron protoporphyrin IX and hemoglobin binding by Porphyromonas gingivalis

Porphyromonas gingivalis, an obligate anerobe with a growth requirement for iron protoporphyrin IX (FePPIX), is exposed to increased temperatures in t he inflamed periodontal pocket. In this study, P. gingivalis was grown in a chemostat at 37 degreesC (control), 39 degreesC, and 41 degreesC, and exam ined for hemagglutinating (HA) activity, hemoglobin binding and degrading a ctivity, and iron protoporphyrin IX binding. HA activity decreased in cells as the growth temperature increased. Binding of mu -oxo bishaem (dimeric h aem), and Fe(II)- and Fe(III)-monomeric forms was increased in 39 degreesC- grown cells but decreased in 41 degreesC-grown cells compared with controls . Cellular hemoglobin binding and degradation decreased with increased grow th temperature. The decrease in cellular hemagglutination and hemoglobin de gradation occurring with increased growth temperature would limit the poten tial overproduction of toxic monomeric haem molecules. The increased bindin g of mu -oxo bishaem and monomeric forms of FePPIX at 39 degreesC may refle ct a defense strategy against reactive oxidants and a mechanism of dampenin g down the inflammatory response to maintain an ecological balance.