Identification and sequences of the Treponema pallidum flhA, flhF, and orf304 genes

Biological basis for syphilis

Syphilis is a chronic sexually transmitted disease caused by Treponema pallidum subsp. pallidum. Clinical manifestations separate the disease into stages; late stages of disease are now uncommon compared to the preantibiotic era. T. pallidum has an unusually small genome and lacks genes that encode many metabolic functions and classical virulence factors. The organism is extremely sensitive to environmental conditions and has not been continuously cultivated in vitro. Nonetheless, T. pallidum is highly infectious and survives for decades in the untreated host. Early syphilis lesions result from the host's immune response to the treponemes. Bacterial clearance and resolution of early lesions results from a delayed hypersensitivity response, although some organisms escape to cause persistent infection. One factor contributing to T. pallidum's chronicity is the paucity of integral outer membrane proteins, rendering intact organisms virtually invisible to the immune system. Antigenic variation of TprK, a putative surface-exposed protein, is likely to contribute to immune evasion. T. pallidum remains exquisitely sensitive to penicillin, but macrolide resistance has recently been identified in a number of geographic regions. The development of a syphilis vaccine, thus far elusive, would have a significant positive impact on global health.

Molecular characterization of the Treponema denticola fliQ region

A Treponema denticola 4.2 kb DNA region containing four complete genes (orfl, fliQ, fliR, and flhB) and a truncated gene (flhA') was sequenced and analyzed. The deduced amino acid sequences of FliQ, FliR, FlhB and FlhA' have significant homology with bacterial proteins associated with the flagellar export apparatus, whereas the deduced amino acid sequence of Orf1 has homology with an E. coli alcohol dehydrogenase. A putative sigma70-like promoter was identified upstream of fliQ. RT-PCR analysis indicated that fliQ, fliR, flhB and flhA' are co-transcribed independently of orfl, suggesting that the motility-associated genes are components of an operon. The location of the T. denticola fliQ-flhA' genes differs from that of the corresponding T. pallidum and Borrelia burgdorferi genes which are present in the large fla or flgB flagellar operons, respectively.

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 continuously cultivated in vitro. A probe based on the nucleotide sequence of the T. pallidum cheA gene was used to screen a T. pallidum genomic DNA library. A treponemal DNA region containing four open reading frames (orfs) was identified. The proteins encoded by these orfs have significant homology with proteins involved in bacterial chemotaxis. The orfs have been designated cheA, cheW, cheX, and cheY. The cheA, cheW, and cheY genes were individually-cloned and expressed in vitro. The observed molecular mass of each protein correlated well with its predicted molecular mass. Reverse transcriptase-PCR data indicate that cheA through 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 dissemination of T. pallidum in vivo. The presence of a putative che operon strongly suggests that T. pallidum has the potential for a chemotactic response.