In recent years, the study found thatPorphyromonas gingivalistype Ⅸ secretion system (T9SS) is a novel protein secretion system, also known as Por secretion system (PorSS). Unlike the eight protein secretion systems found in the past, the system is a polyprotein complex found only inBacteroides. The secreted proteins have both N- and C-terminus, where the former includes Sec-dependent typeⅠsignals peptide, and the latter contains conserved domains (C-terminal conserved domain, CTD).Porphyromonas gingivalisT9SS includes proteins such as intima, outer membrane, cytoplasm, and cell cycle, including at least 34 proteins containing CTD.Porphyromonas gingivalisT9SS is involved in regulating associated virulence factors including gingivin, fimbriae, lipopolysaccharide, HBP35, CPG70 protein and peptidyl-arginine deiminase. These CTD-containing virulence proteins are localized by T9SS and then released to the extracellular domain, thereby destroying periodontal tissue. Therefore, this review summarizes the research progress on the T9SS ofPorphyromonas gingivalis.
