title: Shedding light on microbial dark matter: a TM6 bacterium as natural endosymbiont of a free-living amoeba.
abstract: The TM6 phylum belongs to the so-called microbial dark matter that gathers uncultivated bacteria detected only via DNA sequencing. Recently, the genome sequence of a TM6 bacterium (TM6SC1) has led to suggest that this bacterium would adopt an endosymbiotic life. In the present paper, free-living amoebae bearing a TM6 strain were isolated from a water network. The amoebae were identified as Vermamoeba vermiformis and the presence of a TM6 strain was detected by polymerase chain reaction and microscopy. The partial sequence of its 16S rRNA gene showed this strain to be closely related to the sequenced TM6SC1 strain. These bacteria displayed a pyriform shape and were found within V. vermiformis. Therefore, these bacteria were named Vermiphilus pyriformis. Interactions studies showed that V. pyriformis was highly infectious and that its relation with V. vermiformis was specific and highly stable. Finally, it was found that V. pyriformis inhibited the encystment of V. vermiformis. Overall, this study describes for the first time an endosymbiotic relationship between a TM6 bacterium and a free-living amoeba in the environment. It suggests that other bacteria of the TM6 phylum might also be endosymbiotic bacteria and may be found in other free-living amoebae or other organisms.
authors.affiliation: Microbiologie de l'Eau & Ecologie, Evolution, Symbiose, Laboratoire Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipes, Université de Poitiers, Poitiers, France.|Direction de la Recherche et du Développement pour la Qualité de l'Eau, R&D Biologie, Eau de Paris, 33, avenue Jean Jaurès, 94200, Ivry sur Seine, Paris, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Delafont
authors.affiliation: Microbiologie de l'Eau & Ecologie, Evolution, Symbiose, Laboratoire Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipes, Université de Poitiers, Poitiers, France.
authors.forename: Ascel
authors.initials: A
authors.lastname: Samba-Louaka
authors.affiliation: Microbiologie de l'Eau & Ecologie, Evolution, Symbiose, Laboratoire Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipes, Université de Poitiers, Poitiers, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Bouchon
authors.affiliation: Direction de la Recherche et du Développement pour la Qualité de l'Eau, R&D Biologie, Eau de Paris, 33, avenue Jean Jaurès, 94200, Ivry sur Seine, Paris, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Moulin
authors.affiliation: Microbiologie de l'Eau & Ecologie, Evolution, Symbiose, Laboratoire Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipes, Université de Poitiers, Poitiers, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Héchard
mesh_terms: D000656:Amoeba / Q000382:microbiology*; D001419:Bacteria / Q000145:classification / Q000235:genetics; D054892:Metagenome; D056186:Metagenomics; D064307:Microbiota; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics; D013559:Symbiosis
chemical_list: D012335:RNA, Ribosomal