Daily bursts of biogenic cyanogen bromide (BrCN) control biofilm formation around a marine benthic diatom

Abstract

The spatial organization of biofilms is strongly regulated by chemical cues released by settling organisms. However, the exact nature of these interactions and the repertoire of chemical cues and signals that micro-organisms produce and exude in response to the presence of competitors remain largely unexplored. Biofilms dominated by microalgae often show remarkable, yet unexplained finescale patchy variation in species composition. Because this occurs even in absence of abiotic heterogeneity, antagonistic interactions might play a key role. Here we show that a marine benthic diatom produces chemical cues that cause chloroplast bleaching, a reduced photosynthetic efficiency, growth inhibition and massive cell death in naturally co-occurring competing microalgae. Using headspace solid phase microextraction (HS-SPME)-GC-MS, we demonstrate that this diatom exudes a diverse mixture of volatile iodinated and brominated metabolites including the natural product cyanogen bromide (BrCN), which exhibits pronounced allelopathic activity. Toxin production is light-dependent with a short BrCN burst after sunrise. BrCN acts as a short-term signal, leading to daily "cleaning" events around the algae. We show that allelopathic effects are H 2 O 2 dependent and link BrCN production to haloperoxidase activity. This strategy is a highly effective means of biofilm control and may provide an explanation for the poorly understood role of volatile halocarbons from marine algae, which contribute significantly to the atmospheric halocarbon budget.allelopathy | chemical ecology | marine ecology | signal molecule

The possible role of bacterial signal molecules N-acyl homoserine lactones in the formation of diatom-biofilm ( Cylindrotheca sp.)

“…Before Cylinthrotheca sp. was stored in the laboratory, axenic diatoms cultures were obtained according to the methods of Vanelslander et al (2012). The exponentially growing Cylindrotheca sp.…”

Halogenation and Vanadium Haloperoxidases

“…Similarly, a VBPO system from L. digitata can deactivate acylated homoserine lactones (the cell-to-cell signaling molecules), and halogenated compounds from this species control the biofilm formation and growth in Gram-negative bacteria (Borchardt et al, 2001;Sala€ un et al, 2012). Another interesting example is the daily bursts of cyanogen bromide produced by marine benthic diatoms to avoid biofilm growth (Vanelslander et al, 2012). This role of VHPO in biofilm control has been further explored for medical purposes, whereby VCPO from C. inaequalis has been shown to have an antimicrobial action on Enterococcus faecalis biofilms (Persoon et al, 2012).…”

Proteomics and Metabolomics of Marine Organisms: Current Strategies and Knowledge

“…In the most-often used approach, such as research into aromas and flavors, sampling by headspace-solid-phase microextraction (HS-SPME) for gas chromatography (GC)-MS analyses was used successfully to demonstrate the exudation of iodinated and brominated metabolites by a diatom (Vanelslander et al, 2012). SPME fibers are available for a variety of adsorbents.…”