Stress response of Porphyromonas gingivalis

The heat shock response of Porphyromonas gingivalis was examined by 1 - and 2-dimensional polyacrylamide gel electrophoresis after metabolic labeling with [¹⁴C]-amino acids. When P. gingivalis cells were shifted from 37° C to 42° C, elevated synthesis of 4 proteins with the apparent molecular weight of 92, 80, 74, and 62 kDa was observed, and synthesis of a 50-kDa protein decreased during heat shock. The 74- and 62-kDa proteins were identified as homologs of Escherichia coli DnaK and GroEL respectively by Western immunoblotting. On 2-dimen-sional Western blots, 2 forms of DnaK and 4 forms of GroEL were identified due to their slightly different isolelectric points. dna K and gro EL gene homologs were identified in several P. gingivalis strains and some other black-pigmented oral species. DnaK and GroEL homolog proteins were induced when P. gingivalis cells were challenged by ethanol. These proteins were not induced by oxidative stress or change in pH.