STIMULATION OF INVITRO GROWTH OF TREPONEMA-DENTICOLA BY EXTRACELLULARGROWTH-FACTORS PRODUCED BY PORPHYROMONAS-GINGIVALIS

Cell-free culture filtrates of Porphyromonas gingivalis grown in Wilki ns-Chalgren broth stimulated the growth of six strains of Treponema de nticola in 1186 broth when compared with the effect of uninoculated WC . The pH of the 1186 broth was not altered by the addition of either c ulture filtrate or WC, and all media were fully reduced prior to inocu lation with T. denticola. Growth was also stimulated by factors precip itated from the culture filtrate with 90% (NH4)2SO4, 50% cold ethanol, or 50% cold acetone, and by factors retained after dialysis of the cu lture filtrate through a membrane with a molecular weight cut-off of 5 0 kDa. Growth factor activity was eliminated by heating of the culture filtrate at 55-degrees-C for 4 h. An ether extract of the culture fil trate containing acetic, butyric, isobutyric, isovaleric, propionic, a nd phenylacetic acids did not stimulate growth. Since subgingival plaq ue from periodontal pockets colonized with T. denticola also contains P. gingivalis, certain extracellular proteins with molecular weights g reater than 50 kDa produced by P. gingivalis may act as growth factors for T denticola in the microenvironment of the periodontal pocket.