title: Functional tradeoffs underpin salinity-driven divergence in microbial community composition.
abstract: Bacterial community composition and functional potential change subtly across gradients in the surface ocean. In contrast, while there are significant phylogenetic divergences between communities from freshwater and marine habitats, the underlying mechanisms to this phylogenetic structuring yet remain unknown. We hypothesized that the functional potential of natural bacterial communities is linked to this striking divide between microbiomes. To test this hypothesis, metagenomic sequencing of microbial communities along a 1,800 km transect in the Baltic Sea area, encompassing a continuous natural salinity gradient from limnic to fully marine conditions, was explored. Multivariate statistical analyses showed that salinity is the main determinant of dramatic changes in microbial community composition, but also of large scale changes in core metabolic functions of bacteria. Strikingly, genetically and metabolically different pathways for key metabolic processes, such as respiration, biosynthesis of quinones and isoprenoids, glycolysis and osmolyte transport, were differentially abundant at high and low salinities. These shifts in functional capacities were observed at multiple taxonomic levels and within dominant bacterial phyla, while bacteria, such as SAR11, were able to adapt to the entire salinity gradient. We propose that the large differences in central metabolism required at high and low salinities dictate the striking divide between freshwater and marine microbiomes, and that the ability to inhabit different salinity regimes evolved early during bacterial phylogenetic differentiation. These findings significantly advance our understanding of microbial distributions and stress the need to incorporate salinity in future climate change models that predict increased levels of precipitation and a reduction in salinity.
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Chris L
authors.initials: CL
authors.lastname: Dupont
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: John
authors.initials: J
authors.lastname: Larsson
authors.affiliation: Informatics Group, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Shibu
authors.initials: S
authors.lastname: Yooseph
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Karolina
authors.initials: K
authors.lastname: Ininbergs
authors.affiliation: Informatics Group, J. Craig Venter Institute, Rockville, Maryland, United States of America.
authors.forename: Johannes
authors.initials: J
authors.lastname: Goll
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Johannes
authors.initials: J
authors.lastname: Asplund-Samuelsson
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: John P
authors.initials: JP
authors.lastname: McCrow
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Narin
authors.initials: N
authors.lastname: Celepli
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Lisa Zeigler
authors.initials: LZ
authors.lastname: Allen
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Ekman
authors.affiliation: Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States of America.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lucas
authors.affiliation: Swedish Institute for the Marine Environment (SIME), University of Gothenburg, Gothenburg, Sweden.
authors.forename: Åke
authors.initials: Å
authors.lastname: Hagström
authors.affiliation: Informatics Group, J. Craig Venter Institute, Rockville, Maryland, United States of America.
authors.forename: Mathangi
authors.initials: M
authors.lastname: Thiagarajan
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Brindefalk
authors.affiliation: Informatics Group, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Richter
authors.affiliation: KTH Royal Institute of Technology, Science for Life Laboratory, School of Biotechnology, Solna, Sweden.
authors.forename: Anders F
authors.initials: AF
authors.lastname: Andersson
authors.affiliation: Informatics Group, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Aaron
authors.initials: A
authors.lastname: Tenney
authors.affiliation: KTH Royal Institute of Technology, Science for Life Laboratory, School of Biotechnology, Solna, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lundin
authors.affiliation: Informatics Group, J. Craig Venter Institute, Rockville, Maryland, United States of America.
authors.forename: Andrey
authors.initials: A
authors.lastname: Tovchigrechko
authors.affiliation: Department of Biodiversity Informatics, Swedish Museum of Natural History, Stockholm, Sweden.
authors.forename: Johan A A
authors.initials: JA
authors.lastname: Nylander
authors.affiliation: Informatics Group, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Daniel
authors.initials: D
authors.lastname: Brami
authors.affiliation: Informatics Group, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Badger
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Allen
authors.affiliation: Informatics Group, J. Craig Venter Institute, Rockville, Maryland, United States of America.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Rusch
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Jeff
authors.initials: J
authors.lastname: Hoffman
authors.affiliation: Center for History of Science, The Royal Swedish Academy of Sciences, Stockholm, Sweden.
authors.forename: Erling
authors.initials: E
authors.lastname: Norrby
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Friedman
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
authors.forename: Jarone
authors.initials: J
authors.lastname: Pinhassi
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California, United States of America.
authors.forename: J Craig
authors.initials: JC
authors.lastname: Venter
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Bergman
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics; D001454:Baltic States; D017753:Ecosystem; D054892:Metagenome; D064307:Microbiota; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S; D054712:Salinity; D012623:Seawater / Q000382:microbiology*; D014871:Water Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S