EFFECTS OF TEMPERATURE STRESS ON EXPRESSION OF FIMBRIAE AND SUPEROXIDE-DISMUTASE BY PORPHYROMONAS-GINGIVALIS

We examined the biosynthesis of fimbriae and superoxide dismutase (SOD ) produced by the periodontopathic bacterium Porphyromonas gingivalis in response to elevated temperature. P. gingivalis 2561, grown at 37 d egrees C to mid-logarithmic phase, was subsequently incubated at 39, 4 1, and 43 degrees C, respectively, to stationary phase. There was no d ifference in the growth of cells at 37 and 39 degrees C. However, at 3 9 degrees C there was a 54% reduction in the amount of fimbrillin (fim briae) as well as decreased expression of mRNA for fimA. On the other hand, under the same conditions, a more than twofold increase in the a mount of SOD activity, as well as in the levels of SOD mRNA, was obser ved. Moreover, cells cultured for 20 h at 39 degrees C showed an 86% d ecrease of fimbrillin protein and a threefold increase in SOD activity . These observations suggest that P. gingivalis may undergo alteration s in its virulence and susceptibility to host immune responses as a re sult of the elevated temperatures found in inflamed periodontal pocket s.