Genome degradation is an ongoing process in Rickettsia
1999 (English)In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, ISSN 0737-403, Vol. 16, no 9, 1178-1191 p.Article in journal (Other academic) Published
To study reductive evolutionary processes in bacterial genomes, we examine sequences in the Rickettsia genomes which are unconstrained by selection and evolve as pseudogenes, one of which is the metK gene, which codes for AdoMet synthetase. Here, we sequenced the metK gene and three surrounding genes in eight different species of the genus Rickettsia. The metK gene was found to contain a high incidence of deletions in six lineages, while the three genes in its surroundings were functionally conserved in all eight lineages. A more drastic example of gene degradation was identified in the metK downstream region, which contained an open reading frame in Rickettsia felis. Remnants of this open reading frame could be reconstructed in five additional species by eliminating sites of frameshift mutations and termination codons. A detailed examination of the two reconstructed genes revealed that deletions strongly predominate over insertions and that there is a strong transition bias for point mutations which is coupled to an excess of GC-to-AT substitutions. Since the molecular evolution of these inactive genes should reflect the rates and patterns of neutral mutations, our results strongly suggest that there is a high spontaneous rate of deletions as well as a strong mutation bias toward AT pairs in the Rickettsia genomes. This may explain the low genomic G + C content (29%), the small genome size (1.1 Mb), and the high noncoding content (24%), as well as the presence of several pseudogenes in the Rickettsia prowazekii genome.
Place, publisher, year, edition, pages
SOC MOLECULAR BIOLOGY EVOLUTION , 1999. Vol. 16, no 9, 1178-1191 p.
IdentifiersURN: urn:nbn:se:uu:diva-85236PubMedID: 10486973OAI: oai:DiVA.org:uu-85236DiVA: diva2:113144
Addresses: Andersson SGE, Uppsala Univ, Biomed Ctr, Dept Mol Evolut, Box 590, S-75124 Uppsala, Sweden. Uppsala Univ, Biomed Ctr, Dept Mol Evolut, S-75124 Uppsala, Sweden.2008-10-172008-10-172014-05-14Bibliographically approved