Ref ID : 7111
Martina Schrallhammer, Michael Schweikert, Adriana Vallesi, Franco Verni, and Giulio Petroni; Detection of a Novel Subspecies of Francisella noatunensis as Endosymbiont of the Ciliate Euplotes raikovi. Microb.Ecol. 61:455-464, 2011
Reprint
In File
Notes
Francisella are facultative intracellular bacteria causing severe disease in a broad range of animals. Two species are notable: Francisella tularensis, the causative organism of tularemia and a putative warfare agent, and Francisella noatunensis, an emerging fish pathogen causing significant losses in wild and farmed fish. Although various aspects of Francisella biology have been intensively studied, their natural reservoir in periods between massive outbreaks remains mysterious. Protists have been suspected to serve as a disguised vector of Francisella and co-culturing attempts demonstrate the some species are able to survive and multiply within protozoan cells. Here, we report the first finding of a natural occurrence of Francisella sp. as a protist endosymbiont. By molecular and morphological approaches, we identified intracellular bacteria localized in a strain of the marine ciliate Euplotes raikovi, isolated from the coast Adriatic Sea. Phylogenetic analysis placed these endosymbionts within the genus Francisella, in close but distinct association with F. noatunensis. We suggest the establishment of a novel subspecies within F. noatunensis and propose the cytoplasmic endosymbiont of E. raikovi as "Candidatus F. noatunensis subsp. endociliophora" supsp. nov.