Effect of temperature on growth, hemagglutination, and protease activity of Porphyromonas gingivalis

Bacteria persisting in periodontal pockets are exposed to elevated temperat ures during periods of inflammation, Temperature is an environmental factor that can modulate gene expression. Consequently, in the present study we e xamined the effect of temperature on the expression of virulence determinan ts by the periodontopathogen, Porphyromonas gingivalis, P. gingivalis W50 w as grown in a complex medium under hemin excess at pH 7.0 and at a constant temperature of either 37, 39, or 41 degrees C; cultures were monitored for protease and hemagglutinin activity. P. gingivalis grew well at all three temperatures. An increase in growth temperature from 37 to 39 degrees C res ulted in a 65% reduction in both total arginine- and lysine-specific activi ties (P < 0.01). A further rise in growth temperature to 41 degrees C led t o even greater reductions in arginine-specific (82%; P < 0.001) and lysine- specific (73%; P < 0.01) activities. These reductions were also associated, vith an altered distribution of individual arginine-specific enzyme isoform s, At 41 degrees C, there was a disproportionate reduction in the level of the heterodimeric RI protease, which also contains adhesin domains. The red uction also correlated with a markedly diminished hemagglutination activity of cells, especially in those grown at 41 degrees C, and a reduced immunor eactivity,vith a monoclonal antibody which recognizes gene products involve d in hemagglutination, Thus, as the environmental temperature increased, P. gingivalis adopted a less aggressive phenotype, while retaining cell popul ation levels, The coordinate down-regulation of virulence gene expression i n response to an environmental cue linked to the intensity of the host infl ammatory response is consistent with the clinically observed cyclical natur e of disease progression in periodontal diseases.