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| 2. |
- Nylund, Göran M., 1974, et al.
(författare)
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Seaweed defence against bacteria: a poly-brominated 2-heptanone from the red alga Bonnemaisonia hamifera inhibits bacterial colonisation
- 2008
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 369, s. 39-50
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Tidskriftsartikel (refereegranskat)abstract
- It has previously been shown that the red alga Bonnemaisonia hamifera is less fouled by bacteria relative to co-occurring seaweeds and that surface extracts of B. hamifera inhibit bacterial growth at natural concentrations. In the present study, we isolated the antibacterial metabolite by bioassay-guided fractionation of extracts of B. hamifera using standard chromatographic methods. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry were used for molecular identification. The antibacterial activity in the extracts was caused by a previously described poly-halogenated 2-heptanone: 1,1,3,3-tetrabromo-2-heptanone. To further investigate the role of this compound as an ecologically relevant antifoulant against bacterial colonisation, we quantified it on the surface of B. hamifera specimens collected in the field. Levels of 1,1,3,3-tetrabromo-2-heptanone on the surface of the algae were on average 3.6 µg cm–2. Natural surface concentrations of this secondary metabolite were used to test for growth-inhibiting effects against 18 bacterial strains isolated from red algae co-occurring with B. hamifera. The test indicated a phylogenetic specificity of the metabolite, and gram-positive bacteria and flavobacteria proved to be particularly sensitive. In a further test, natural surface concentrations of 1,1,3,3-tetrabromo-2-heptanone were applied to artificial panels and incubated in the sea. After 4 and 7 d, the number of settled bacteria was significantly lower on all treated panels compared to controls. Thus, this study shows that 1,1,3,3-tetrabromo-2-heptanone has an ecologically relevant role as an antifoulant against bacterial colonisation on the surface of B. hamifera. This study is also one of only a few to quantify natural surface concentrations of a seaweed secondary metabolite.
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| 3. |
- Nylund, Göran M., 1974, et al.
(författare)
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The red alga Bonnemaisonia asparagoides regulates epiphytic bacterial abundance and community composition by chemical defence
- 2010
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 71:1, s. 84-93
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Tidskriftsartikel (refereegranskat)abstract
- Ecological research on algal-derived metabolites with antimicrobial activity has recently received increased attention and is no longer only aimed at identifying novel natural compounds with potential use in applied perspectives. Despite this progress, few studies have so far demonstrated ecologically relevant antimicrobial roles of algal metabolites, and even fewer have utilized molecular tools to investigate the effects of these metabolites on the natural community composition of bacteria. In this study, we investigated whether the red alga Bonnemaisonia asparagoides is chemically defended against bacterial colonization of its surface by extracting surface-associated secondary metabolites and testing their antibacterial effects. Furthermore, we compared the associated bacterial abundance and community composition between B. asparagoides and two coexisting macroalgae. Surface extracts tested at natural concentrations had broad-spectrum effects on the growth of ecologically relevant bacteria, and consistent with this antibacterial activity, natural populations of B. asparagoides had significantly lower densities of epibacteria compared with the coexisting algae. Terminal restriction fragment length polymorphism analysis further showed that B. asparagoides harboured surface-associated bacteria with a community composition that was significantly different from those on coexisting macroalgae. Altogether, these findings demonstrate that B. asparagoides produces surface-bound antibacterial compounds with a significant impact on the abundance and composition of the associated bacterial community.
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- Persson, Frank, 1970, et al.
(författare)
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Ecological role of a seaweed secondary metabolite for a colonizing bacterial community
- 2011
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Ingår i: Biofouling. - : Informa UK Limited. - 0892-7014 .- 1029-2454. ; 27:6, s. 579-588
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria associated with seaweeds can both harm and benefit their hosts. Many seaweed species are known to produce compounds that inhibit growth of bacterial isolates, but the ecological role of seaweed metabolites for the associated bacterial community structure is not well understood. In this study the response of a colonizing bacterial community to the secondary metabolite (1,1,3,3-tetrabromo-2-heptanone) from the red alga Bonnemaisonia hamifera was investigated by using field panels coated with the metabolite at a range of concentrations covering those measured at the algal surface. The seaweed metabolite has previously been shown to have antibacterial effects. The metabolite significantly affected the natural fouling community by (i) altering the composition, (ii) altering the diversity by increasing the evenness and (iii) decreasing the density, as measured by terminal restriction fragment length polymorphism in conjunction with clone libraries of the 16S rRNA genes and by bacterial enumeration. No single major bacterial taxon (phylum, class) was particularly affected by the metabolite. Instead changes in community composition were observed at a more detailed phylogenetic level. This indicates a broad specificity of the seaweed metabolite against bacterial colonization, which is supported by the observation that the bacterial density was significantly affected at a lower concentration (0.02 μg cm -2) than the composition (1-2.5 μg cm -2) and the evenness (5 μg cm -2) of the bacterial communities. Altogether, the results emphasize the role of secondary metabolites for control of the density and structure of seaweed-associated bacterial communities.
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