Chemical defence against bacteria in the red alga Asparagopsis armata: linking structure with function

Paul, N.A., de Nys, Rocky, and Steinberg, P.D. (2006) Chemical defence against bacteria in the red alga Asparagopsis armata: linking structure with function. Marine Ecology Progress Series, 306. pp. 87-101.

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Abstract

Although numerous algal products have antimicrobial activity, limited knowledge of metabolite localisation and presentation in algae has meant that ecological roles of algal natural products are not well understood. In this study, extracts of Asparagopsis armata had antibacterial activity against marine (Vibrio spp.) and biomedical (Escherichia coli, Pseudomonas aeruginosa and Staphylococcus spp.) strains. The major natural products in both life-history stages of A. armata (as determined by gas chromatography-mass spectrometry analysis [GC-MS]) were bromoform (0.58 to 4.3% of dry weight [DW]) and dibromoacetic acid [DBA] (0.02 to 2.6% DW), and each compound was active against these same bacteria. To resolve whether this antibiotic activity was ecologically relevant, we examined the localisation of metabolites in the specialised cells of A. armata and observed a delivery mechanism for the release of metabolites to the surface. Bromoform and DBA were subsequently quantified in the surrounding medium of laboratory cultures, establishing their release from the alga. In a novel ecological test of algal natural products, halogenated metabolites in A. armata were manipulated by omitting bromine from an artificial seawater medium. Significantly higher densities of epiphytic bacteria occurred on algae that no longer produced halogenated metabolites. Both bromoform and DBA were more active against bacteria isolated from algae lacking brominated metabolites than algae producing normal amounts of these compounds. Taken together, these results indicate that halogenated metabolites of A. armata may be important in reducing epiphytic bacterial densities.

Item ID: 3990
Item Type: Article (Refereed Research - C1)
Keywords: chemical defence; antifouling; algai; bacteria; gland cell; bromoform; dibromoacetic acid; gas chromatography-mass spectrometry
ISSN: 1616-1599
Date Deposited: 26 Oct 2009 01:42
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
Citation Count from Web of Science Web of Science 59
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Last 12 Months: 25
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