The Porphyromonas gingivalis clpB gene is involved in cellular invasion in vitro and virulence in vivo


  • Present address: Lihui Yuan, Department of Physiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA.

  • Editor: Patrik Bavoil

Correspondence: Ann Progulske-Fox, Department of Oral Biology, Center for Molecular Microbiology, College of Dentistry, University of Florida, PO Box 100424, Gainesville, FL 32610-0424, USA. Tel.: +1 352 846 0770; fax: +1 352 392 2361; e-mail:


ClpB, a component of stress response in microorganisms, serves as a chaperone, preventing protein aggregation and assisting in the refolding of denatured proteins. A clpB mutant of Porphyromonas gingivalis W83 demonstrated increased sensitivity to heat stress, but not to hydrogen peroxide and extreme pHs. In KB cells, human coronary artery endothelial (HCAE) cells and gingival epithelial cells, the clpB mutant exhibited significantly decreased invasion suggesting that the ClpB protein is involved in cellular invasion. Transmission electron microscopic analysis showed that the clpB mutant was more susceptible to intracellular killing than the wild-type strain in HCAE cells. The global genetic profile of the clpB mutant showed that 136 genes belonging to several different cellular function groups were differentially regulated, suggesting that ClpB is ultimately involved in the expression of multiple P. gingivalis genes. A competition assay in which a mixture of wild-type W83 and the clpB mutant were injected into mice demonstrated that the clpB mutant did not survive as well as the wild type. Additionally, mice treated with the clpB mutant alone survived significantly better than those treated with the wild-type strain. Collectively, these data suggest that ClpB, either directly or indirectly, plays an important role in P. gingivalis virulence.