Treponema pallidum subsp. pallidum str. Nichols

Treponema pallidum, is a helical to sinusoidal spirochaete with 2 membranes, a thin peptidoglycan layer and flagella that lie in the periplasmic space. It is the causative agent of syphilis, plays a role in the transmission and acquisition of HIV, and is a major cause of stillbirth and perinatal morbidity in the developing world. Even if the primary infection is localized, bacteria rapidly disseminate and cause manifestations in the cardiovascular and nervous systems. It is an obligate human parasite.The first T.pallidum strain to be sequenced was strain Nichols, which was isolated in 1912 from the cerebrospinal fluid of patient with secondary syphilis. It has since been passed in rabbits for nearly a century. This Chicago strain was isolated in 1951, has not been passed continually in rabbits and has had an important role in research on antigenic variation, immune escape and pathogen persistence. There are 44 nucleotide substitutions, 21 deletions and 75 insertions compared to the Nichols genome (adapted from PMID). (EBI Integr8)