title: "Candidatus Paraholospora nucleivisitans", an intracellular bacterium in Paramecium sexaurelia shuttles between the cytoplasm and the nucleus of its host.
abstract: An intracellular bacterium was discovered in two isolates of Paramecium sexaurelia from an aquarium with tropical fish in Münster (Germany) and from a pond in the Wilhelma zoological-botanical garden, Stuttgart (Germany). The bacteria were regularly observed in the cytoplasm of the host, but on some occasions they were found in the macronucleus of the host cell. In these cases, only a few, if any, bacteria were observed remaining in the cytoplasm. The bacterium was not infectious to P. sexaurelia or other species of Paramecium and appeared to be an obligate intracellular bacterium, while bacteria-free host cells were completely viable. The fluorescence in situ hybridisation (FISH) and comparative 16SrDNA sequence analyses showed that the bacterium belonged to a new genus, and was most closely, yet quite distantly, related to Holospora obtusa. In spite of this relationship, the new bacteria differed from Holospora by at least two biological features. Whereas all Holospora species reside exclusively in the nuclei of various species of Paramecium and show a life cycle with a morphologically distinct infectious form, for the new bacterium no infectious form and no life cycle have been observed. For the new bacterium, the name Candidatus Paraholospora nucleivisitans is suggested. The host P. sexaurelia is usually known from tropical and subtropical areas and is not a species typically found in Germany and central Europe. Possibly, it had been taken to Germany with fish or plants from tropical or subtropical waters. Candidatus Paraholospora nucleivisitans may therefore be regarded as an intracellular neobacterium for Germany.
authors.affiliation: Universität Stuttgart, Biologisches Institut, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
authors.forename: Erik
authors.initials: E
authors.lastname: Eschbach
authors.forename: Martin
authors.initials: M
authors.lastname: Pfannkuchen
authors.forename: Michael
authors.initials: M
authors.lastname: Schweikert
authors.forename: Denja
authors.initials: D
authors.lastname: Drutschmann
authors.forename: Franz
authors.initials: F
authors.lastname: Brümmer
authors.forename: Sergei
authors.initials: S
authors.lastname: Fokin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ludwig
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Görtz
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000382:microbiology*; D016000:Cluster Analysis; D003593:Cytoplasm / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005858:Germany; D042281:Holosporaceae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D010247:Paramecium / Q000382:microbiology*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S