title: A specific and widespread association between deep-sea Bathymodiolus mussels and a novel family of Epsilonproteobacteria.
abstract: Bathymodiolus mussels dominate animal communities at many hydrothermal vents and cold seeps. Essential to the mussels' ecological and evolutionary success is their association with symbiotic methane- and sulfur-oxidizing gammaproteobacteria, which provide them with nutrition. In addition to these well-known gammaproteobacterial endosymbionts, we found epsilonproteobacterial sequences in metatranscriptomes, metagenomes and 16S rRNA clone libraries as well as by polymerase chain reaction screening of Bathymodiolus species sampled from vents and seeps around the world. These epsilonproteobacterial sequences were closely related, indicating that the association is highly specific. The Bathymodiolus-associated epsilonproteobacterial 16S rRNA sequences were at most 87.6% identical to the closest cultured relative, and 91.2% identical to the closest sequences in public databases. This clade therefore represents a novel family within the Epsilonproteobacteria. Fluorescence in situ hybridization and transmission electron microscopy showed that the bacteria are filamentous epibionts associated with the gill epithelia in two Bathymodiolus species. In animals that host highly specific symbioses with one or a few types of endosymbionts, other less-abundant members of the microbiota can be easily overlooked. Our work highlights how widespread and specific associations with less-abundant microbes can be. Possibly, these microbes play an important role in the survival and health of their animal hosts.
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.
authors.forename: Adrien
authors.initials: A
authors.lastname: Assié
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Borowski
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.
authors.forename: Karina
authors.initials: K
authors.lastname: van der Heijden
authors.affiliation: CIGoM, Instituto de Biotecnologia, UNAM, Av. Universidad 2001, C.P.62210, Cuernavaca, Morelos, Mexico.
authors.forename: Luciana
authors.initials: L
authors.lastname: Raggi
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Geier
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Leisch
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.
authors.forename: Mario P
authors.initials: MP
authors.lastname: Schimak
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.|MARUM, University of Bremen, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Dubilier
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany.|Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstr. 14, Vienna, 1090, Austria.
authors.forename: Jillian M
authors.initials: JM
authors.lastname: Petersen