T. pallidum, a spirochete and the cause of syphilis, is a helical microorganism with a thin peptidoglycan coat and a flagellum that resides within the periplasmic space. In the tissue culture, T. pallidum require only glucose, maltose and mannose for multiplication. T. pallidum is an obligate parasite and derives many nutrients from its host. For example, T. pallidum lacks a respiratory electron transport chain. ATP production is accomplished by substrate-level phosphorylation. In the July 17, 1998 issue of Science, Fraser et al. reported the complete genome sequence of Treponema Pallidum. The T. pallidum genome consists of 1,138,006 base pairs and contains 1041 predicted open reading frames (ORF). Four hundred seventy-six ORFs in T. pallidum have orthologs in B. burgdorferi, the cause of Lyme disease. More than 40% of the orthologous genes in these bacteria are highly conserved and are present in other bacteria. One hundred fifteen of the ORFs shared in the two bacteria, encode proteins of unknown biological function and almost 50% of these are unique to spirochetes. T. pallidum has 44 tRNA species. These are organized into eight clusters of 25 genes as well as 19 single genes and two rRNA operons. Additional features of the genome were revealed by this study. The average G and C content of the genome is 52.8% and the average size of the open reading frames is 1023 base pairs. The average size of bacterial proteins is 37,771 Daltons. It became apparent that potential virulence factors exist in the T. pallidum genome which includes a family of 12 potential membrane proteins and several putative hemolysins. The sequences that drive the DNA replication, transcription, translation, and repair were found in the T. pallidum genome. A small number of identifiable transporters was present. However, phosphoenolpyruvate:phosphotransferase carbohydrate transporters were not found. The T. pallidum genome encodes a pathway for the conversion of phosphoenolpyruvate or pyruvate through oxaloacetate to aspartate, which is then converted to glutamate. The findings also revealed differences between the T. pallidum and the B. burgdorferi. For example, 572 ORFs in the T. pallidum are not shared with B. burgdorferi. In contrast to the B. burgdorferi , T. pallidum lacks genes which encode superoxide dismutase, catalase or peroxidase. Thus, the findings provide support for presence of common genes as well as a considerable diversity among pathogenic spirochetes

FIGURE LEGEND:

Figure 1. Treponema pallidum genome. The figure in the middle shows the stained microorganism in a tissue section.

REFERENCE:

Fraser CM, Norris SJ, Weinstock GM, White O, Sutton GG, Dodson R, Gwinn M, Hickey EK, Clayton R, Ketchum KA, Sodergren E, Hardham JM, McLeod MP, Salzberg S, Peterson J, Khalak H, Richardson D, Howell JK, Chidambaram M, Utterback T, McDonald L, Artiach P, Bowman C, Cotton MD, Venter JC, et al: Complete genome sequence of Treponema pallidum, the syphilis spirochete. Science 1998 Jul 17;281(5375):375-388

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