title: Flagellar movement in two bacteria of the family rickettsiaceae: a re-evaluation of motility in an evolutionary perspective.
abstract: Bacteria of the family Rickettsiaceae have always been largely studied not only for their importance in the medical field, but also as model systems in evolutionary biology. In fact, they share a recent common ancestor with mitochondria. The most studied species, belonging to genera Rickettsia and Orientia, are hosted by terrestrial arthropods and include many human pathogens. Nevertheless, recent findings show that a large part of Rickettsiaceae biodiversity actually resides outside the group of well-known pathogenic bacteria. Collecting data on these recently described non-conventional members of the family is crucial in order to gain information on ancestral features of the whole group. Although bacteria of the family Rickettsiaceae, and of the whole order Rickettsiales, are formally described as non-flagellated prokaryotes, some recent findings renewed the debate about this feature. In this paper we report the first finding of members of the family displaying numerous flagella and active movement inside their host cells. These two new taxa are hosted in aquatic environments by protist ciliates and are described here by means of ultrastructural and molecular characterization. Data here reported suggest that the ancestor of Rickettsiales displayed flagellar movement and re-evaluate the hypothesis that motility played a key-role in the origin of mitochondria. Moreover, our study highlights that the aquatic environment represents a well exploited habitat for bacteria of the family Rickettsiaceae. Our results encourage a deep re-consideration of ecological and morphological traits of the family and of the whole order.
authors: Biology Department, University of Pisa, Pisa, Italy.
authors: Claudia
authors: C
authors: Vannini
authors: Biology Department, University of Pisa, Pisa, Italy.
authors: Vittorio
authors: V
authors: Boscaro
authors: Biology Department, University of Pisa, Pisa, Italy.
authors: Filippo
authors: F
authors: Ferrantini
authors: Department of Cytology and Histology, St.-Petersburg State University, St.-Petersburg, Russia.
authors: Konstantin A
authors: KA
authors: Benken
authors: Department of Cytology and Histology, St.-Petersburg State University, St.-Petersburg, Russia.
authors: Timofei I
authors: TI
authors: Mironov
authors: Biological Institute, Stuttgart University, Stuttgart, Germany.
authors: Michael
authors: M
authors: Schweikert
authors: Biological Institute, Stuttgart University, Stuttgart, Germany.
authors: Hans-Dieter
authors: HD
authors: Görtz
authors: Biology Department, University of Pisa, Pisa, Italy ; Department of Invertebrate Zoology, St.-Petersburg State University, St.-Petersburg, Russia.
authors: Sergei I
authors: SI
authors: Fokin
authors: Department of Cytology and Histology, St.-Petersburg State University, St.-Petersburg, Russia.
authors: Elena V
authors: EV
authors: Sabaneyeva
authors: Biology Department, University of Pisa, Pisa, Italy.
authors: Giulio
authors: G
authors: Petroni
mesh_terms: D044822:Biodiversity; D005075:Biological Evolution; D005407:Flagella / Q000502:physiology*; D006801:Humans; D012287:Rickettsiaceae / Q000502:physiology*; D013045:Species Specificity