Reductive genome evolution from the mother of Rickettsia.

ABSTRACT: The Rickettsia genus is a group of obligate intracellular alpha-proteobacteria representing a paradigm of reductive evolution. Here, we investigate the evolutionary processes that shaped the genomes of the genus. The reconstruction of ancestral genomes indicates that their last common ancestor contained more genes, but already possessed most traits associated with cellular parasitism. The differences in gene repertoires across modern Rickettsia are mainly the result of differential gene losses from the ancestor. We demonstrate using computer simulation that the propensity of loss was variable across genes during this process. We also analyzed the ratio of nonsynonymous to synonymous changes (Ka/Ks) calculated as an average over large sets of genes to assay the strength of selection acting

SUBMITTER: Blanc G 

PROVIDER: S-EPMC1779305 | biostudies-literature | 2007 Jan

REPOSITORIES: biostudies-literature