Porphyromonas gingivalis is a Gram negative pathogenic oral bacterium, characterized by a number of virulence factors that contribute to the progression of periodontitis. P. gingivalis secretes outer membrane vesicles (OMVs) which are spherical structures that result from “blebbing” of the outer membrane of the cell. OMVs serve as secretory vehicles containing lipids and proteins that aid progression of periodontitis. Cryo electron microscopy and proteomic analysis shows P. gingivalis cells and vesicles are surrounded by an electron dense layer (EDSL) rich in anionic lipopolysaccharide attached virulence proteins, including the arginine-specific cysteine proteinases RgpA and RgpB.
PG1879 is a putative patatin-like protein. Patatins were originally identified in potatoes as a plant storage glycoprotein with phospholipase activity and are typically associated with cleavage of fatty acids from membrane lipids. Patatin-like proteins have been identified in plants, eukaryotes, fungi, archea and are widely found in bacterial genomes. The aim of this study was to determine the effect of PG1879 mutation on P. gingivalis whole cell and OMV surface layer characteristics.
A P. gingivalis W50 isogenic deletion mutant of PG1879, designated W50::PG1879-, was constructed by homologous recombination. Arginine-specific cysteine-proteinase activity assays have demonstrated a significant reduction in arginine-specific gingipain activity in W50::PG1879- whole cell, vesicle and vesicle-free supernatant extracts when compared with wild type values. Cryo- electron micrograph results produced images of a reduced EDSL in W50::PG1879- cells when compared with wild type P. gingivalis, showing that PG1879 has a role in modification of the EDSL of P. gingivalis.