IDENTIFICATION, SEQUENCES, AND EXPRESSION OF TREPONEMA-PALLIDUM CHEMOTAXIS GENES

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.