General Information and Genome of Porphyromonas gingivalis - Nonmotile, Gram-negative, rod-shaped, anaerobic bacterium - Forms black colonies on blood agar - Found in the oral cavity, upper gastrointestinal tract, respiratory tract, and colon - Implicated in periodontal disease and bacterial vaginosis - Linked to Alzheimer's disease and rheumatoid arthritis - Described in 2003 - Contains 1,990 open reading frames - Encoded by 2,343,479 bp - Average G+C content of 48.3% - Estimated 463 essential genes

Virulence Factors of Porphyromonas gingivalis - Gingipain enzymes (Arg-gingipain and Lys-gingipain) - Gingipains contribute to survival, virulence, and nutrient collection - Gingipains degrade host peptides and proteins for nitrogen and carbon sources - Gingipains facilitate adhesion, invasion, and colonization - Gingipains degrade host immune response signals and cytokines

Capsular Polysaccharide (CPS) of Porphyromonas gingivalis - Encapsulated strain is more virulent than nonencapsulated strain - CPS downregulates proinflammatory cytokine production - CPS elicits host immune responses and inflammation in periodontitis - Vaccines made from P. gingivalis CPS impair oral bone loss - CPS-challenged macrophages express cell migration chemokines

Fimbriae of Porphyromonas gingivalis - Fimbriae are appendages involved in cellular attachment - Fimbriae contribute to adhesion, invasion, and colonization - Fimbriae bind to integrins and impair host cell homeostatic controls - Long fimbriae mediate initial attachment and biofilm organization - Short fimbriae are essential for cell-cell aggregation and microcolony formation

Evasion of Host Defenses and Immune Responses - P. gingivalis evades host immune responses through gingipain proteases. - P. gingivalis uses a capsular polysaccharide to evade host immune responses. - P. gingivalis induces host cell proliferation to evade immune responses. - P. gingivalis cleaves chemokines responsible for neutrophil recruitment, affecting immune response. - P. gingivalis down-regulates IL-8 induction, causing delayed neutrophil recruitment. - P. gingivalis modulates leukocyte recruitment by proteolysis of cytokines and chemokines. - Arg-gingipain and lys-gingipains are responsible for proteolysis of cytokines and chemokines. - P. gingivalis impairs signaling by cleaving IgG 1 and 3, evading opsonophagocytosis from PMNs. - P. gingivalis subverts the complement pathway through C5αR and C3αR, modulating leukocyte killing capacity. - P. gingivalis inhibits pro-inflammatory and antimicrobial responses in human monocytes and mouse macrophages. - P. gingivalis inhibits apoptosis by modulating the JAK/Stat pathway. - P. gingivalis compromises the integrity of the epithelial cell layer, allowing for invasion and colonization. - P. gingivalis causes a microbial shift in the oral cavity, leading to uncontrolled growth of commensal bacteria. - P. gingivalis colocalizes with CD4+ T cells in human biopsies, indicating a potential infection mechanism. - P. gingivalis increases the virulence of other commensal bacteria in both in vivo and in vitro experiments. - P. gingivalis plays an important role in the onset of chronic adult periodontitis. - P. gingivalis disrupts host tissue homeostasis and adaptive immune response. - Laser capture microdissection plus qRT-PCR detects P. gingivalis in human biopsies. - The infection mechanism of T cells by P. gingivalis remains unknown. - P. gingivalis alone cannot induce periodontitis.