title: Defence chemistry modulation by light and temperature shifts and the resulting effects on associated epibacteria of Fucus vesiculosus.
abstract: The goals of this study were (1) to investigate whether Fucus vesiculosus regulates the production of its antifouling defence chemicals against epibacteria in response to light limitation and temperature shifts and (2) to investigate if different surface concentrations of defence compounds shape epibacterial communities. F. vesiculosus was incubated in indoor mesocosms at five different temperature conditions (5 to 25°C) and in outdoor mesocosms under six differently reduced sunlight conditions (0 to 100%), respectively. Algal surface concentrations of previously identified antifouling compounds--dimethylsulphopropionate (DMSP), fucoxanthin and proline--were determined and the bacterial community composition was characterized by in-depth sequencing of the 16S-rRNA gene. Altogether, the effect of different treatment levels upon defence compound concentrations was limited. Under all conditions DMSP alone appeared to be sufficiently concentrated to warrant for at least a partial inhibitory action against epibiotic bacteria of F. vesiculosus. In contrast, proline and fucoxanthin rarely reached the necessary concentration ranges for self-contained inhibition. Nonetheless, in both experiments along with the direct influence of temperature and light, all three compounds apparently affected the overall bacterial community composition associated with F. vesiculosus since tendencies for insensitivity towards all three compounds were observed among bacterial taxa that typically dominate those communities. Given that the concentrations of at least one of the compounds (in most cases DMSP) were always high enough to inhibit bacterial settlement, we conclude that the capacity of F. vesiculosus for such defence will hardly be compromised by shading or warming to temperatures up to 25°C.
authors.affiliation: Department of Benthic Ecology, Helmholtz-Zentrum für Ozeanforschung (GEOMAR), Kiel, Germany.
authors.forename: Mahasweta
authors.initials: M
authors.lastname: Saha
authors.affiliation: Institute for Inorganic and Analytical Chemistry Bioorganic Analytics, Friedrich-Schiller-Universität Jena, Jena, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Rempt
authors.affiliation: Department of Benthic Ecology, Helmholtz-Zentrum für Ozeanforschung (GEOMAR), Kiel, Germany.
authors.forename: Stephanie B
authors.initials: SB
authors.lastname: Stratil
authors.affiliation: Department of Benthic Ecology, Helmholtz-Zentrum für Ozeanforschung (GEOMAR), Kiel, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wahl
authors.affiliation: Institute for Inorganic and Analytical Chemistry Bioorganic Analytics, Friedrich-Schiller-Universität Jena, Jena, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Pohnert
authors.affiliation: Department of Benthic Ecology, Helmholtz-Zentrum für Ozeanforschung (GEOMAR), Kiel, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Weinberger
mesh_terms: D001419:Bacteria / Q000235:genetics; D018441:Biofilms; D044645:Fucus / Q000737:chemistry* / Q000378:metabolism / Q000382:microbiology*; D008027:Light; D059013:Microbial Consortia / Q000235:genetics / Q000502:physiology; D011392:Proline / Q000032:analysis / Q000378:metabolism; D012336:RNA, Ribosomal, 16S; D013452:Sulfonium Compounds / Q000032:analysis / Q000378:metabolism; D013696:Temperature; D024341:Xanthophylls / Q000032:analysis / Q000378:metabolism
chemical_list: D012336:RNA, Ribosomal, 16S; D013452:Sulfonium Compounds; D024341:Xanthophylls; C025164:fucoxanthin; D011392:Proline; C068078:dimethylpropiothetin