Journal of Molecular Evolution

, Volume 63, Issue 1, pp 120–126 | Cite as

Thermal Adaptation of the Small Subunit Ribosomal RNA Gene: A Comparative Study

  • Huai-Chun Wang
  • Xuhua Xia
  • Donal Hickey


We carried out a comprehensive survey of small subunit ribosomal RNA sequences from archaeal, bacterial, and eukaryotic lineages in order to understand the general patterns of thermal adaptation in the rRNA genes. Within each lineage, we compared sequences from mesophilic, moderately thermophilic, and hyperthermophilic species. We carried out a more detailed study of the archaea, because of the wide range of growth temperatures within this group. Our results confirmed that there is a clear correlation between the GC content of the paired stem regions of the 16S rRNA genes and the optimal growth temperature, and we show that this correlation cannot be explained simply by phylogenetic relatedness among the thermophilic archaeal species. In addition, we found a significant, positive relationship between rRNA stem length and growth temperature. These correlations are found in both bacterial and archaeal rRNA genes. Finally, we compared rRNA sequences from warm-blooded and cold-blooded vertebrates. We found that, while rRNA sequences from the warm-blooded vertebrates have a higher overall GC content than those from the cold-blooded vertebrates, this difference is not concentrated in the paired regions of the molecule, suggesting that thermal adaptation is not the cause of the nucleotide differences between the vertebrate lineages.


Small subunit ribosomal RNA Secondary structure Phylogenetic independent contrast GC content Optimal growth temperature 



This work was supported by a Research Grant from NSERC Canada (D.A.H.) and an Ontario Graduate Scholarship (H.C.W.). We thank Dr. N. Galtier and two reviewers for their comments.

Supplementary material

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Supplementary material


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Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  1. 1.Department of Mathematics and StatisticsDalhousie UniversityHalifaxCanada
  2. 2.Department of BiologyUniversity of OttawaOttawaCanada
  3. 3.Department of BiologyConcordia UniversityMontrealCanada

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