RT Journal Article
SR Electronic
T1 The extracellular association of the bacterium “<em>Candidatus</em> Deianiraea vastatrix” with the ciliate <em>Paramecium</em> suggests an alternative scenario for the evolution of <em>Rickettsiales</em>
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 479196
DO 10.1101/479196
A1 M. Castelli
A1 E. Sabaneyeva
A1 O. Lanzoni
A1 N. Lebedeva
A1 A.M. Floriano
A1 S. Gaiarsa
A1 K. Benken
A1 L. Modeo
A1 C. Bandi
A1 A. Potekhin
A1 D. Sassera
A1 G. Petroni
YR 2018
UL http://biorxiv.org/content/early/2018/11/27/479196.abstract
AB Rickettsiales are a lineage of obligatorily intracellular Alphaproteobacteria, encompassing important human pathogens, manipulators of host reproduction, and mutualists. Here we report the discovery of a novel Rickettsiales bacterium associated with Paramecium, displaying a unique extracellular lifestyle, including the ability to replicate outside host cells. Genomic analyses show that the bacterium possesses a higher capability to synthesize amino acids, compared to all investigated Rickettsiales. Considering these observations, phylogenetic and phylogenomic reconstructions, and re-evaluating the different means of interaction of Rickettsiales bacteria with eukaryotic cells, we propose an alternative scenario for the evolution of intracellularity in Rickettsiales. According to our reconstruction, the Rickettsiales ancestor would have been an extracellular and metabolically versatile bacterium, while obligate intracellularity and genome reduction would have evolved later in parallel and independently in different sub-lineages. The proposed new scenario could impact on the open debate on the lifestyle of the last common ancestor of mitochondria within Alphaproteobacteria.