Journal of Molecular Evolution

, Volume 48, Issue 6, pp 723–739

Detection of Seven Major Evolutionary Lineages in Cyanobacteria Based on the 16S rRNA Gene Sequence Analysis with New Sequences of Five Marine Synechococcus Strains

  • Daiske  Honda
  • Akira  Yokota
  • Junta  Sugiyama

DOI: 10.1007/PL00006517

Cite this article as:
Honda, D., Yokota, A. & Sugiyama, J. J Mol Evol (1999) 48: 723. doi:10.1007/PL00006517

Abstract.

Although molecular phylogenetic studies of cyanobacteria on the basis of the 16S rRNA gene sequence have been reported, the topologies were unstable, especially in the inner branchings. Our analysis of 16S rRNA gene phylogeny by the maximum-likelihood and neighbor-joining methods combined with rate homogeneous and heterogeneous models revealed seven major evolutionary lineages of the cyanobacteria, including prochlorophycean organisms. These seven lineages are always stable on any combination of these methods and models, fundamentally corresponding to phylogenetic relationships based on other genes, e.g., psbA, rbcL, rnpB, rpoC, and tufA. Moreover, although known genotypic and phenotypic characters sometimes appear paralleled in independent lineages, many characters are not contradictory within each group. Therefore we propose seven evolutionary groups as a working hypothesis for successive taxonomic reconstruction. New 16S rRNA sequences of five unicellular cyanobacterial strains, PCC 7001, PCC 7003, PCC 73109, PCC 7117, and PCC 7335 of Synechococcus sp., were determined in this study. Although all these strains have been assigned to ``marine clusters B and C,'' they were separated into three lineages. This suggests that the organisms classified in the genus Synechococcus evolved diversely and should be reclassified in several independent taxonomic units. Moreover, Synechococcus strains and filamentous cyanobacteria make a monophyletic group supported by a comparatively high statistical confidence value (80 to 100%) in each of the two independent lineages; therefore, these monophylies probably reflect the convergent evolution of a multicellular organization.

Key words: Cyanobacteria —Synechococcus— Phylogeny — Ribosomal RNA — Maximum-likelihood method — Neighbor-joining method — Rate homo- and heterogeneous models

Copyright information

© Springer-Verlag New York Inc. 1999

Authors and Affiliations

  • Daiske  Honda
    • 1
  • Akira  Yokota
    • 1
  • Junta  Sugiyama
    • 1
  1. 1.Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-0032, JapanJP