<unk>  belongs to the phylum Bacteroidota and is a nonmotile, Gram-negative, rod-shaped, anaerobic, pathogenic bacterium. It forms black colonies on blood agar. It is found in the oral cavity, where it is implicated in periodontal disease, as well as in the upper gastrointestinal tract, the respiratory tract and the colon. It has been isolated from women with bacterial vaginosis. Collagen degradation observed in chronic periodontal disease results in part from the collagenase enzymes of this species. It has been shown in an in vitro study that P.<unk>  can invade human gingival fibroblasts and can survive in the presence of antibiotics. P.<unk>  invades gingival epithelial cells in high numbers, in which case both bacteria and epithelial cells survive for extended periods of time. High levels of specific antibodies can be detected in patients harboring P.<unk> . P.<unk>  infection has been linked to Alzheimer's disease and rheumatoid arthritis. It contains the enzyme peptidyl-arginine deiminase, which is involved in citrullination. Patients with rheumatoid arthritis have increased incidence of periodontal disease; antibodies against the bacterium are significantly more common in these patients. P.<unk>  is divided into K-serotypes based upon capsular antigenicity of the various types. These serotypes have been the drivers of observations regarding bacterial cell to cell interactions to the associated serotype-dependent immune response and risk with pancreatic cancer.
Porphyromonas gingivalis
Neisseria mucosa
Entamoeba gingivalis
Prevotella intermedia
Helicobacter suis
Aggregatibacter actinomycetemcomitans
Mansonella perstans
Prevotella bivia