Plant Biol (Stuttg) 2005; 7(5): 526-532
DOI: 10.1055/s-2005-865912
Research Paper

Georg Thieme Verlag Stuttgart KG · New York

Genetic Evidence of “American” and “European” Type Symbiotic Algae of Paramecium bursaria Ehrenberg

R. Hoshina1 , Y. Kato1 , S. Kamako1 , N. Imamura1
  • 1Department of Bio Science and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Noji Higashi 1-1-1 Kusatsu Shiga, Japan 525 - 8577
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Received: June 23, 2005

Accepted: June 29, 2005

15. September 2005 (online)


Paramecium bursaria is composed of a “host” ciliate and a “symbiont” green alga. Based upon physiology, DNA hybridization and virus infection, two types of symbionts, called “American” type and “European” type, have been reported to date. Here, we determined the 18S rDNA and internal transcribed spacer 2 (ITS2) regions for both “American” and “European” types. Sequence features clearly separated into two lineages; NC64A (USA), Syngen 2-3 (USA), Cs2 (Chinese), MRBG1 (Australian), and Japanese strains belong to the “American”, whereas PB-SW1 (German) and CCAP 1660/11 (British) strains belong to the “European”. In “American” 18S rDNA, three introns were inserted in the same positions as for previously described Japanese symbionts. In “European” 18S rDNA, a single intron occurred in a different position than in the “American”. Between the types, sequence differences were seven or eight nucleotides (0.39 %) in the 18S rDNA exon, and more than 48 nucleotides (19.2 %) in ITS2 regions. We subsequently sequenced the host 18S rDNA. As a result, two groups: Cs2, MRBG1, and Japanese strains, and PB-SW1 and CCAP 1660/11 strains, were separated (with 23 substitutions and 4 insertions or deletions between the groups). The congruent separations between hosts and symbionts may imply that the type of symbiont depends on the host type.


N. Imamura

Department of Bio Science and Biotechnology
Faculty of Science and Engineering
Ritsumeikan University

Noji Higashi 1-1-1 Kusatsu Shiga

Japan 525-8577


Editor: F. Salamini