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Marine Ecology Progress Series

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MEPS 178:271-280 (1999)  -  doi:10.3354/meps178271

Phylogenetic diversity of bacterial endosymbionts in the gutless marine oligochete Olavius loisae (Annelida)

Nicole Dubilier1,*, Rudolf Amann1, Christer Erséus2, Gerard Muyzer1, SueYong Park3, Olav Giere4, Colleen M. Cavanaugh3

1Molecular Ecology Group, Max Planck Institute of Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany
2Department of Invertebrate Zoology, Swedish Museum of Natural History, S-104 05 Stockholm, Sweden
3Department of Organismic and Evolutionary Biology, Harvard University, The Biological Laboratories, Cambridge, Massachusetts 02138, USA
4Zoologisches Institut und Zoologisches Museum, University of Hamburg, D-20146 Hamburg, Germany

ABSTRACT: Endosymbiotic associations with more than 1 bacterial phylotype are rare among chemoautotrophic hosts. In gutless marine oligochetes 2 morphotypes of bacterial endosymbionts occur just below the cuticle between extensions of the epidermal cells. Using phylogenetic analysis, in situ hybridization, and denaturing gradient gel electrophoresis based on 16S ribosomal RNA genes, it is shown that in the gutless oligochete Olavius loisae, the 2 bacterial morphotypes correspond to 2 species of diverse phylogenetic origin. The larger symbiont belongs to the gamma subclass of the Proteobacteria and clusters with other previously described chemoautotrophic endosymbionts. The smaller symbiont represents a novel phylotype within the alpha subclass of the Proteobacteria. This is distinctly different from all other chemoautotrophic hosts with symbiotic bacteria which belong to either the gamma or epsilon Proteobacteria. In addition, a third bacterial morphotype as well as a third unique phylotype belonging to the spirochetes was discovered in these hosts. Such a phylogenetically diverse assemblage of endosymbiotic bacteria is not known from other marine invertebrates.

KEY WORDS: Symbiosis · Chemoautotrophic bacteria · Oligochaeta · 16S rRNA

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