title: Top-down and bottom-up control on bacterial diversity in a western Norwegian deep-silled fjord.
abstract: We investigated the relationship between viruses and co-occurring bacterial communities in the Sognefjord, a deep-silled fjord in Western Norway. A combination of flow cytometry and automated ribosomal intergenic spacer analysis (ARISA) was used to assess prokaryote and viral abundances, and bacterial diversity and community composition, respectively, in depth profiles and at two different sampling seasons (November and May). With one exception, bacterial diversity did not vary between samples regardless of depth or season. The virus and prokaryote abundances as well as bacterial community composition, however, varied significantly with season and depth, suggesting a link between the Sognefjord viral community and potential bacterial host community diversity. To our knowledge, these findings provide the first description of microbial communities in the unique Sognefjord ecosystem, and in addition are in agreement with the simple model version of the 'Killing the Winner' theory (KtW), which postulates that microbial community diversity is a feature that is essentially top-down controlled by viruses, while community composition is bottom-up controlled by competition for limiting growth substrates.
authors.affiliation: Department of Biology, University of Bergen, Thormøhlensgt 53A, N-5006, Bergen, Norway.
authors.forename: Julia E
authors.initials: JE
authors.lastname: Storesund
authors.affiliation: Department of Biology, University of Bergen, Thormøhlensgt 53A, N-5006, Bergen, Norway.
authors.forename: Svein Rune
authors.initials: SR
authors.lastname: Erga
authors.affiliation: Uni Research AS, Uni Research Environment, Thormøhlensgt 49B, N-5006 Bergen, Norway.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Ray
authors.affiliation: Department of Biology, University of Bergen, Thormøhlensgt 53A, N-5006, Bergen, Norway.
authors.forename: T Frede
authors.initials: TF
authors.lastname: Thingstad
authors.affiliation: Department of Biology, University of Bergen, Thormøhlensgt 53A, N-5006, Bergen, Norway Ruth.Sandaa@bio.uib.no.
authors.forename: Ruth-Anne
authors.initials: RA
authors.lastname: Sandaa
mesh_terms: D001419:Bacteria / Q000235:genetics* / Q000254:growth & development*; D044822:Biodiversity; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D017753:Ecosystem; D063366:Estuaries; D059013:Microbial Consortia / Q000235:genetics*; D009664:Norway; D012621:Seasons; D014780:Viruses / Q000235:genetics* / Q000254:growth & development
chemical_list: D021903:DNA, Ribosomal Spacer
keywords: ARISA; Killing the Winner; Sognefjorden; flow cytometry; host–virus interactions; virus