Molecular characterization of the obligate endosymbiont "Caedibacter macronucleorum" Fokin and Görtz, 1993 and of its host Paramecium duboscqui strain Ku4-8

Martina Schrallhammer, Sergei I. Fokin, Karl Heinz Schleifer, Giulio Petroni

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Bacterial endosymbionts of protozoa were often described as new species by protozoologists mainly on the basis of few morphological characters and partly by host specificity. Many of these species have never been validated by prokaryotic microbiologists whose taxonomic rules are quite different from those of protozoologists, who use the Zoological Code of Nomenclature. "Caedibacter macronucleorum" Fokin and Görtz 1993, an endosymbiont of Paramecium duboscqui, belongs to this category. Here we provide the molecular characterization of this organism and of its host P. duboscqui strain Ku4-8. Bacterial 16S rRNA gene sequence analysis proved that "C. macronucleorum" belongs to the Alphaproteobacteria. It is closely related to Caedibacter caryophilus but not to Caedibacter taeniospiralis, which belongs to the Gammaproteobacteria. "Caedibacter macronucleorum" and C. caryophilus 16S rRNA genes show a similarity value of 99%. This high 16S rRNA sequence similarity and the lack of a specific oligonucleotide probe for distinguishing the two endosymbionts do not allow validating "C. macronucleorum" as a provisional taxon (Candidatus). Nevertheless, "C. macronucleorum" and C. caryophilus can be easily discriminated on the basis of a highly variable stretch of nucleotides that interrupts the 16S rRNA genes of both organisms.

Original languageEnglish
Pages (from-to)499-506
Number of pages8
JournalJournal of Eukaryotic Microbiology
Volume53
Issue number6
DOIs
StatePublished - Nov 2006

Keywords

  • Ciliophora
  • Endocytobiont
  • Holosporaceae
  • Internal excised element
  • Intracellular bacteria
  • Kappa particles
  • Killer trait
  • R-body
  • SSU rRNA
  • Species boundaries

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