Treponema denticola

Treponema denticola is a Gram-negative, obligate anaerobic, motile and highly proteolytic spirochete bacterium. It dwells in a complex and diverse microbial community within the oral cavity and is highly specialized to survive in this environment. T. denticola is associated with the incidence and severity of human periodontal disease. Having elevated T. denticola levels in the mouth is considered one of the main etiological agents of periodontitis. T. denticola is related to the syphilis-causing obligate human pathogen, Treponema pallidum subsp. pallidum. It has also been isolated from women with bacterial vaginosis. The first genome of T. denticola to be sequenced was strain 35405 which was initially isolated and designated as the type strain by Chan et al. The 2,843,201-bp genome sequence encodes 2,786? open reading frames (ORFs) as well a 6 rRNAs and 44 tRNAs. This is in stark contrast to the minimal genome of Treponema pallidum which encodes only 1,040 ORFs. The native cellular architecture of the bacterial cell was revealed using cryo-electron tomography, a technique observing intact plunge-frozen cells. Tightly organized bundles of periplasmic flagella were observed in the periplasm, a characteristic of spirochetes. The tapering of the cell ends, conserved between cells, encompass a patella-shaped structure observed in the periplasm at the cell tip. This structure might be involved in the polar attachment of the cells. Cytoplasmic filaments, a bacterial intermediate-like filaments composed of the protein CfpA, are adjacent to the inner membrane and run parallel to the tightly organized flagellar filaments. Those cytoplasmic filaments are critical for pathogenicity, directly or indirectly as they are also involved in chromosome structure, segregation, or the cell division processes. The absence of either flagella or cytoplasmic filaments in deficient mutant increase the mouse peritoneal macrophages in vitro uptake.