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MEPS 249:39-51 (2003)
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Abstract
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16S rDNA-based phylogeny of sulphur-oxidising bacterial endosymbionts in marine bivalves from cold-seep habitats
Johannes F. Imhoff1,*, Heiko Sahling2, Jörg Süling1, Thomas Kath1
1Institut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany
2GEOMAR Research Center for Marine Geoscience, Wischhofstraße 1-3, 24148 Kiel, Germany
*Email: jimhoff@ifm.uni-kiel.de
ABSTRACT: The phylogenetic relationship of sulphur-oxidising endosymbiotic bacteria from bivalves of the families Vesicomyidae (Calyptogena sp. C1, Calyptogena sp. C3), Solemyidae (Acharax sp.) and Thyasiridae (Conchocele
sp.) from cold-seep habitats were determined by 16S rDNA nucleotide sequence analyses. The endosymbiotic bacteria form distinct groups within the gamma-Proteobacteria and are well separated from each other and from free-living sulphur-oxidising
bacteria of the genera Beggiatoa, Halothiobacillus and Thiomicrospira. The endosymbiotic bacteria of Acharax sp. from cold seeps off Oregon, Indonesia and Pakistan have sequences highly similar to each other but quite distinct
from other thiotrophic endosymbionts. This includes endosymbionts from Solemya spp., to which they are distantly related. Symbiotic bacteria of Conchocele sp. from a cold seep in the Sea of Okhotsk are similar to those of Bathymodiolus
thermophilus and related species, as shown by their overall sequence similarity and by signature sequences. The endosymbiotic bacteria of Calyptogena spp. from cold seeps off Oregon and Pakistan are closely related to those of other
vesicomyids. Endosymbiont species found off Oregon corresponded to 2 different clusters of Calyptogena spp. symbionts in the same samples. The results corroborate the hypothesis of a monophyletic origin of the symbionts in vesicomyid clams, and
support the existence of deeply branching groups in solemyid symbionts and of divergent lines and distribution for thyasirid symbionts. The results also indicate that certain symbiont species cluster according to the depth distribution of their hosts, and
that in consequence host species together with their symbionts may have undergone depth-specific adaptation and evolution.
KEY WORDS: Endosymbiotic sulphur bacteria · Bacterial phylogeny · Cold seeps · Acharax · Conchocele · Calyptogena
Full text in pdf format
Published in MEPS Vol.
249
(2003) on March 10
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2003
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