Comparative Genomics of Spirochetes
Steven J. Norris and George M. Weinstock
from: Pathogenic Treponema: Molecular and Cellular Biology (Edited by: Justin D. Radolf and Sheila A. Lukehart). Caister Academic Press, U.K. (2006)
Abstract
The recent sequencing of the genomes of several spirochetes permits a thorough analysis of the similarities and differences within this bacterial phylum. Treponema pallidum subsp. pallidum has one of the smallest bacterial genomes at 1.14 million base pairs (Mb) and has limited metabolic capabilities, reflecting its adaptation through genome reduction to the rich environment of mammalian tissue. Comparison with the genome of Treponema denticola reveals that, despite its larger genome size (2.84 Mb), it also has limited biosynthetic activities and is highly dependent on the gingival crevice microenvironment to provide required nutrients. The two Borrelia species sequenced to date also have limited 'core' metabolic functions encoded on a 0.91 Mb linear chromosome, but have acquired multiple plasmids that are important in their survival in the tick midgut and mammalian or avian species and in transmission between these two environments. The larger genomes of the two Leptospira interrogans strains sequenced (4.6 Mb) are highly similar and reflect extensive biosynthetic ATP production mechanisms consistent with its ability to live free in the environment as well as infect and cause disease in mammals. Information to date indicates that the genus Treponema evolved from a common ancestor early in bacterial evolution (perhaps hundreds of millions of years ago), whereas the T. pallidum subspecies are closely related and may have diverged within tens of thousands of years read more ...
