title: Host-microbe interactions as a driver of acclimation to salinity gradients in brown algal cultures.
abstract: Like most eukaryotes, brown algae live in association with bacterial communities that frequently have beneficial effects on their development. Ectocarpus is a genus of small filamentous brown algae, which comprises a strain that has recently colonized freshwater, a rare transition in this lineage. We generated an inventory of bacteria in Ectocarpus cultures and examined the effect they have on acclimation to an environmental change, that is, the transition from seawater to freshwater medium. Our results demonstrate that Ectocarpus depends on bacteria for this transition: cultures that have been deprived of their associated microbiome do not survive a transfer to freshwater, but restoring their microflora also restores the capacity to acclimate to this change. Furthermore, the transition between the two culture media strongly affects the bacterial community composition. Examining a range of other closely related algal strains, we observed that the presence of two bacterial operational taxonomic units correlated significantly with an increase in low salinity tolerance of the algal culture. Despite differences in the community composition, no indications were found for functional differences in the bacterial metagenomes predicted to be associated with algae in the salinities tested, suggesting functional redundancy in the associated bacterial community. Our study provides an example of how microbial communities may impact the acclimation and physiological response of algae to different environments, and thus possibly act as facilitators of speciation. It paves the way for functional examinations of the underlying host-microbe interactions, both in controlled laboratory and natural conditions.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, Roscoff, France.
authors.forename: Simon M
authors.identifier: http://orcid.org/0000-0001-7987-7523
authors.initials: SM
authors.lastname: Dittami
authors.affiliation: Institut de Recherche Thérapeutique de l'Université de Nantes, UMR 1087, Plateforme Génomique, Nantes, France.
authors.forename: Laëtitia
authors.initials: L
authors.lastname: Duboscq-Bidot
authors.affiliation: Plateforme de Séquençage-Génotypage, FR 2424 CNRS UPMC, Station Biologique, CS 90074, Roscoff, France.
authors.forename: Morgan
authors.initials: M
authors.lastname: Perennou
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, Roscoff, France.
authors.forename: Angélique
authors.initials: A
authors.lastname: Gobet
authors.affiliation: ABiMS platform, FR 2424 CNRS UPMC, Station Biologique, Roscoff, France.
authors.forename: Erwan
authors.initials: E
authors.lastname: Corre
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, Roscoff, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Boyen
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, Roscoff, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Tonon
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D001419:Bacteria / Q000235:genetics; D005618:Fresh Water / Q000382:microbiology*; D054892:Metagenome; D056265:Microbial Interactions / Q000235:genetics / Q000502:physiology*; D064307:Microbiota / Q000235:genetics; D000459:Phaeophyceae / Q000382:microbiology* / Q000502:physiology; D055049:Salt Tolerance / Q000235:genetics / Q000502:physiology; D012623:Seawater / Q000382:microbiology*