Article
Nature 396, 133-140 (12 November 1998) | doi:10.1038/24094; Received 21 July 1998; Accepted 24 September 1998
The genome sequence of Rickettsia prowazekii and the origin of mitochondria
Siv G. E. Andersson1, Alireza Zomorodipour1, Jan O. Andersson1, Thomas Sicheritz-Pontén1, U. Cecilia M. Alsmark1, Raf M. Podowski1, A. Kristina Näslund1, Ann-Sofie Eriksson1, Herbert H. Winkler2 & Charles G. Kurland1
- Department of Molecular Biology, University of Uppsala, Uppsala S-75124, Sweden
- Department of Microbiology and Immunology, University of South Alabama, Mobile, Alabama 36688, USA
Correspondence to: Charles G. Kurland1
Correspondence and requests for materials should be addressed
to C.G.K.
(e-mail: Email: chuck@xray.bmc.uu.se).
Abstract
We describe here the complete genome sequence (1,111,523 base pairs) of the obligate intracellular parasite Rickettsia prowazekii, the causative agent of epidemic typhus. This genome contains 834 protein-coding genes. The functional profiles of these genes show similarities to those of mitochondrial genes: no genes required for anaerobic glycolysis are found in either R. prowazekii or mitochondrial genomes, but a complete set of genes encoding components of the tricarboxylic acid cycle and the respiratory-chain complex is found in R. prowazekii. In effect, ATP production in Rickettsia is the same as that in mitochondria. Many genes involved in the biosynthesis and regulation of biosynthesis of amino acids and nucleosides in free-living bacteria are absent from R. prowazekii and mitochondria. Such genes seem to have been replaced by homologues in the nuclear (host) genome. The R. prowazekii genome contains the highest proportion of non-coding DNA (24%) detected so far in a microbial genome. Such non-coding sequences may be degraded remnants of 'neutralized' genes that await elimination from the genome. Phylogenetic analyses indicate that R. prowazekii is more closely related to mitochondria than is any other microbe studied so far.
