Identification of the bacterial endosymbionts of the marine ciliate Euplotes magnicirratus (Ciliophora, Hypotrichia) and proposal of 'Candidatus Devosia euplotis' .

摘要

This paper reports the identification of bacterial endosymbionts that inhabit the cytoplasmof the marine ciliated protozoon Euplotes magnicirratus. Ultrastructural and full-cycle rRNAapproaches were used to reveal the identity of these bacteria. Based on analysis of 16S rRNAgene sequences, evolutionary trees were constructed; these placed the endosymbiont in thegenus Devosia in the a-Proteobacteria. The validity of this finding was also shown by fluorescencein situ hybridization with a Devosia-specific oligonucleotide probe. Differences at the 16S rRNAgene level (which allowed the construction of a species-specific oligonucleotide probe) and thepeculiar habitat indicate that the endosymbiont represents a novel species. As its cultivation hasnot been successful to date, the provisional name ‘Candidatus Devosia euplotis’ is proposed.The species- and group-specific probes designed in this study could represent convenienttools for the detection of ‘Candidatus Devosia euplotis’ and Devosia-like bacteria in theenvironment.