Journal of Molecular Evolution

, Volume 58, Issue 6, pp 633–641 | Cite as

Evidence for Recombination in the Microcystin Synthetase (mcy) Genes ofToxic Cyanobacteria Microcystis spp

  • Yuuhiko Tanabe
  • Kunimitsu Kaya
  • Makoto M. WatanabeEmail author


Recombination has been suggested to be an important factor for the genetic variation of bacterial genes, but few studies have dealt with intragenic recombination between the same or closely related species of cyanobacteria. Here we provide strong evidence for recombination in the microcystin synthetase (mcy) gene cluster of the toxic cyanobacteria Microcystis spp. This gene cluster contains 10 genes (mcyA to J) that encode a mixed polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) complex. mcy gene sequences were determined for four selected regions (within mcyA, D, G, and J) within the mcy gene cluster from 1 Canadian and 10 Asian toxic Microcystis and compared with previously published mcy sequences. Split decomposition analysis indicated a reticulate phylogeny of mcyA, and several potential recombination tracts of mcyA were identified by the RDP analysis and a runs test implemented in GENECONV. In contrast, no recombination was detected in the mcyD, G, and J sequences. However, discrepancies among the four mcy gene genealogies were evident from the results of independent split decomposition analyses, which were further supported by incongruence length difference (ILD) tests. Taken together, these findings suggest that both intragenic and intergenic recombination within the mcy gene cluster contributes to the genetic diversity of the mcy genes of Microcystis spp.


Cyanobacteria Microcystin synthetase Microcystis NRPS Recombination Split decomposition 



We thank S. Otsuka for providing several Microcystis strains, T. Sano for providing unpublished data of toxin contents of Microcystis strains, C. Duenrut for isolating the T20-3 strain, and F. Kasai and M. Kawachi for making helpful suggestions. We also thank the staff of the Microbial Culture Collection at National Institute for Environmental Studies for helpful advice on culturing Microcystis strains.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Yuuhiko Tanabe
    • 1
  • Kunimitsu Kaya
    • 1
  • Makoto M. Watanabe
    • 1
    Email author
  1. 1.Environmental Biology DivisionNational Institute for Environmental StudiesTsukubaJapan

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