Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, 9000 Ghent, Belgium.
Proc Natl Acad Sci U S A. 2012 Feb 14;109(7):2412-7. doi: 10.1073/pnas.1108062109. Epub 2012 Jan 30.
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 fine-scale 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.
生物膜的空间组织受定居生物释放的化学信号的强烈调节。然而，这些相互作用的确切性质以及微生物产生和分泌的应对竞争的化学信号和化学物质的种类在很大程度上仍未得到探索。由微藻主导的生物膜通常表现出显著的、但尚未解释的物种组成的小尺度斑块变化。由于这种现象即使在没有非生物异质性的情况下也会发生，因此拮抗相互作用可能起着关键作用。在这里，我们表明一种海洋底栖硅藻会产生化学信号，导致叶绿体漂白、光合作用效率降低、生长抑制和大量细胞死亡，而这些在自然共存的竞争微藻中发生。我们使用顶空固相微萃取（HS-SPME）-GC-MS 表明，这种硅藻会散发出多种挥发性碘代和溴代代谢物的混合物，包括天然产物氰溴化物（BrCN），它表现出明显的化感活性。毒素的产生依赖于光，在日出后会有一个短暂的 BrCN 爆发。BrCN 作为一种短期信号，导致藻类周围每天发生“清洁”事件。我们表明，化感效应依赖于 H(2)O(2)，并将 BrCN 的产生与过氧化物酶活性联系起来。这种策略是一种非常有效的生物膜控制手段，可能为海洋藻类释放的挥发性卤代烃的作用提供了一个解释，这些卤代烃对大气卤代烃预算有重要贡献。
