Surface properties and ultrastructure of Porphyromonas gingivalis W50 and pleiotropic mutants

Functions of S-layers

Although S-layers are being increasingly identified on Bacteria and Archaea, it is enigmatic that in most cases S-layer function continues to elude us. In a few instances, S-layers have been shown to be virulence factors on pathogens (e.g. Campylobacter fetus ssp. fetus and Aeromonas salmonicida), protective against Bdellovibrio, a depository for surface-exposed enzymes (e.g. Bacillus stearothermophilus), shape-determining agents (e.g. Thermoproteus tenax) and nucleation factors for fine-grain mineral development (e.g. Synechococcus GL 24). Yet, for the vast majority of S-layered bacteria, the natural function of these crystalline arrays continues to be evasive. The following review up-dates the functional basis of S-layers and describes such diverse topics as the effect of S-layers on the Gram stain, bacteriophage adsorption in lactobacilli, phagocytosis by human polymorphonuclear leukocytes, the adhesion of a high-molecular-mass amylase, outer membrane porosity, and the secretion of extracellular enzymes of Thermoanaerobacterium. In addition, the functional aspect of calcium on the Caulobacter S-layer is explained.

A novel mouse model to study the virulence of and host response to Porphyromonas (Bacteroides) gingivalis

We describe here the development of a mouse subcutaneous chamber model that allows for the examination of host-parasite interactions as well as the determination of gross pathology with Porphyromonas (Bacteroides) gingivalis challenge. When inoculated into stainless-steel chambers implanted subcutaneously in female BALB/c mice, P. gingivalis W83, W50, and A7436 (10(8) to 10(10) CFU) caused cachexia, ruffling, general erythema and phlegmonous, ulcerated, necrotic lesions, and death. P. gingivalis W50/BEI, HG405, and 33277 (10(10) CFU) produced localized abscesses in the mouse chamber model with rejection of chambers at the injection site. Analysis of chamber fluid from 33277-, HG405-, and W50/BEI-infected mice by cytocentrifugation revealed inflammatory cell debris, polymorphonuclear leukocytes, and high numbers of dead bacteria. In contrast, fluid from A7436-, W50-, and W83-infected mice revealed infiltration predominantly of polymorphonuclear leukocytes and live bacteria. Bacteria were found primarily associated with polymorphonuclear leukocytes in the fluid from W50-, HG405-, and W83-infected mice but not from A7436-infected mice. Viable isolates were recoverable from the chamber fluid through day 3 for W50/BEI, day 5 for 33277, day 6 for HG405, day 7 for W50, day 14 for W83, and day 26 for A7436. All strains induced a systemic immunoglobulin G response in serum and chamber fluid samples. The use of this model will allow us to examine the virulence of P. gingivalis as defined by the interaction of host response to localized infection with P. gingivalis.

Hemin levels in culture medium of Porphyromonas (Bacteroides) gingivalis regulate both hemin binding and trypsinlike protease production

Washed cells and Sarkosyl-insoluble outer membrane preparations of the black-pigmented bacteroides Porphyromonas gingivalis W50 bound hemin. The amount of hemin removed from a buffered solution by both cells and outer membranes was significantly larger if bacteria had been grown in broths supplemented with 5 mg of hemin per liter rather than none. Conversely, cells grown without supplemental hemin bound relatively little. However, all preparations bound some hemin. In addition, hemin regulated the production of significantly higher levels of trypsinlike protease by P. gingivalis W50. The nonpigmented variant, W50 BE1, showed no such responses to the levels of hemin in the growth medium.