Virulence factors of Treponema denticola

Spirochetes were first observed in the oral cavity in humans by van Leeuwenhoek (34, 101, 102, 182).Spirochetes are gram-negative microorganisms with long spiral-shaped cells which achieve motility by means of periplasmic flagella (Fig. 1).Members of the phylum "Spirochaetes" include the etiologic agents of syphilis, Lyme disease and other borrelial relapsing fevers.The phylum consists of Spirochaetaceae, Serpulinaceae and Leptospiraceae (3, 39).The first group consists of Spirochaeta, Borrelia, Clevelandina, Cristispira, Diplocalyx, Hollandina, Pillotina and Treponema.Among these, only the genus Treponema has been isolated from the oral cavity.Treponemes have been detected from a variety of environments such as the human oral cavity, the digestive tracts of cattle and termite guts (48,53, 133, 177).Treponema share many characteristics with gram-positive bacteria, and recent phylogenetic studies have shown that spirochaetes form a single cluster distinct from both gram-positive and