Dimethylsulphopropionate (DMSP) and proline from the surface of the brown algaFucus vesiculosusinhibit bacterial attachment

Abstract

It was demonstrated previously that polar and non-polar surface extracts of the brown alga Fucus vesiculosus collected during winter from the Kiel Bight (Germany) inhibited bacterial attachment at natural concentrations. The present study describes the bioassay-guided identification of the active metabolites from the polar fraction. Chromatographic separation on a size-exclusion liquid chromatography column and bioassays identified an active fraction that was further investigated using nuclear magnetic resonance spectroscopy and mass spectrometry. This fraction contained the metabolites dimethylsulphopropionate (DMSP), proline and alanine. DMSP and proline caused the anti-attachment activity. The metabolites were further quantified on the algal surface together with its associated boundary layer. DMSP and proline were detected in the range 0.12-1.08 ng cm(-2) and 0.09-0.59 ng cm(-2), respectively. These metabolites were tested in the concentration range from 0.1 to 1000 ng cm(-2) against the attachment of five bacterial strains isolated from algae and sediment co-occurring with F. vesiculosus. The surface concentrations for 50% inhibition of attachment of these strains were always <0.38 ng cm(-2) for DMSP and in four cases <0.1 ng cm(-2) for proline, while one strain required 1.66 ng cm(-2) of proline for 50% inhibition. Two further bacterial strains that had been directly isolated from F. vesiculosus were also tested, but proved to be the least sensitive. This study shows that DMSP and proline have an ecologically relevant role as surface inhibitors against bacterial attachment on F. vesiculosus.

Defence Chemistry Modulation by Light and Temperature Shifts and the Resulting Effects on Associated Epibacteria of Fucus vesiculosus

“…In previous studies with field collected material, DMSP has been detected on Fucus surfaces at concentrations in the range of 0.12 to 1.08 ng cm −2 [12]. In the present study, differently temperature treated samples of Fucus contained DMSP at similar concentrations, with the highest concentrations at 20°C (Fig.…”

“…Concentrations that were previously reported [10], [12] for field collected apical tips (or whole algal individuals in the case of fucoxanthin) are also given, as well as previously reported necessary concentrations for halfmaximal inhibition (EC50) of various marine bacterial isolates [10], [12].…”

“…Artificial substrates containing surface extracts of this alga maintain microbial communities that are relatively similar to those associated with F. vesiculosus [11]. Furthermore, the alga harbours at its surface fucoxanthin, dimethylsulfopropionate (DMSP) and proline, which all reduce bacterial settlement [10], [12]. This activity is strain-specific and while many strains are repelled by those compounds, others can be attracted [12].…”

“…Furthermore, the alga harbours at its surface fucoxanthin, dimethylsulfopropionate (DMSP) and proline, which all reduce bacterial settlement [10], [12]. This activity is strain-specific and while many strains are repelled by those compounds, others can be attracted [12]. Thus, the mentioned repellents not only influence bacterial density but also have the potential to influence epibacterial community composition on Fucus as certain strains are attracted and others deterred.…”

“…To answer this question, surface concentrations of fucoxanthin, DMSP and proline were quantified after different temperature and light treatments. To evaluate the potential effect of changing concentrations upon microbial settlers two different approaches were chosen: (1) Detected concentrations were compared to the known necessary doses for half maximal settlement inhibition of potential bacterial colonisers of Fucus [10], [12]; and (2) detected concentrations were correlated to the relative abundance of major bacterial groups, that were identified in both experiments by in-depth sequencing of the 16S-rRNA gene. The concentration of mannitol, the main primary energy storage compound of Fucus , was used to quantify the degree of light limitation stress.…”