Treponema pallidum, the agent of syphilis, is a pathogenic spirochete
that has no known mechanisms of genetic exchange and cannot be continu
ously cultivated in vitro. A probe based on the nucleotide sequence of
the T. pallidum cheA gene was used to screen a T. pallidum genomic DN
A library. A treponemal DNA region containing four open reading frames
(orfs) was identified. The proteins encoded by these orfs have signif
icant homology with proteins involved in bacterial chemotaxis. The orf
s have been designated cheA, cheW, cheX, and cheY. The cheA, cheW, and
cheY genes were individually cloned and expressed in vitro. The obser
ved molecular mass of each protein correlated well with its predicted
molecular mass. Reverse transcriptase-PCR data indicate that cheA thro
ugh cheY are co-transcribed. The organization of these genes suggests
that they comprise an operon. We hypothesize that the ability to sense
and respond to nutrient gradients is important for the survival and d
issemination of T. pallidum in vivo. The presence of a putative che op
eron strongly suggests that T. pallidum has the potential for a chemot
actic response.