Stock Frederike, Bilcke Gust, De Decker Sam, Osuna-Cruz Cristina Maria, Van den Berge Koen, Vancaester Emmelien, De Veylder Lieven, Vandepoele Klaas, Mangelinckx Sven, Vyverman Wim
Research group Protistology and Aquatic Ecology, Department of Biology, Faculty of Sciences, Ghent University, Ghent, Belgium.
Department of Applied Mathematics, Computer Science and Statistics, Faculty of Sciences, Ghent University, Ghent, Belgium.
Front Microbiol. 2020 Jun 9;11:1240. doi: 10.3389/fmicb.2020.01240. eCollection 2020.
In aquatic habitats, diatoms are frequently found in association with Proteobacteria, many members of which employ cell-to-cell communication via -acyl homoserine lactones (AHLs). It has been suggested that diatoms could distinguish between beneficial and algicidal bacteria in their surroundings by sensing AHLs. Although some microalgae can interfere with AHL signaling, e.g., by releasing AHL mimics or degrading them, molecular responses to AHLs in microalgae are still unclear. Therefore, we tested the effects of short-chained AHLs, i.e., -hexanoyl homoserine lactone (C6-HSL), -3-hydroxyhexanoyl homoserine lactone (OH-C6-HSL), and -3-oxohexanoyl homoserine lactone (oxo-C6-HSL) and long-chained AHLs, i.e., -tetradecanoyl homoserine lactone (C14-HSL), -3-hydroxytetradecanoyl homoserine lactone (OH-C14-HSL), and -3-oxotetradecanoyl homoserine lactone (oxo-C14-HSL), on growth of the benthic diatom . All tested short-chained AHLs did not affect diatom growth, while long-chained AHLs promoted (C14-HSL) or inhibited (OH-C14-HSL and oxo-C14-HSL) growth. To investigate the physiological effects of these long-chained AHLs in more detail, an RNA-seq experiment was performed during which was treated with the growth-promoting C14-HSL and the growth-inhibiting oxo-C14-HSL. One tetramic acid was also tested (TA14), a structural rearrangement product of oxo-C14-HSL, which also induced growth inhibition in . After 3 days of treatment, analysis revealed that 3,410 genes were differentially expressed in response to at least one of the compounds. In the treatment with the growth-promoting C14-HSL many genes involved in intracellular signaling were upregulated. On the other hand, exposure to growth-inhibiting oxo-C14-HSL and TA14 triggered a switch in lipid metabolism towards increased fatty acid degradation. In addition, oxo-C14-HSL led to downregulation of cell cycle genes, which is in agreement with the stagnation of cell growth in this treatment. Combined, our results indicate that bacterial signaling molecules with high structural similarity induce contrasting physiological responses in .
在水生栖息地中，经常发现硅藻与变形菌门相关联，其中许多成员通过N-酰基高丝氨酸内酯（AHLs）进行细胞间通讯。有人提出，硅藻可以通过感知AHLs来区分周围环境中的有益细菌和杀藻细菌。尽管一些微藻可以干扰AHL信号传导，例如通过释放AHL模拟物或降解它们，但微藻对AHLs的分子反应仍不清楚。因此，我们测试了短链AHLs，即N-己酰高丝氨酸内酯（C6-HSL）、N-3-羟基己酰高丝氨酸内酯（OH-C6-HSL）和N-3-氧代己酰高丝氨酸内酯（oxo-C6-HSL）以及长链AHLs，即N-十四酰高丝氨酸内酯（C14-HSL）、N-3-羟基十四酰高丝氨酸内酯（OH-C14-HSL）和N-3-氧代十四酰高丝氨酸内酯（oxo-C14-HSL）对底栖硅藻生长的影响。所有测试的短链AHLs均不影响硅藻生长，而长链AHLs则促进（C14-HSL）或抑制（OH-C14-HSL和oxo-C14-HSL）生长。为了更详细地研究这些长链AHLs的生理效应，在实验中用促进生长的C14-HSL和抑制生长的oxo-C14-HSL处理了[硅藻名称未给出]。还测试了一种四嗪酸（TA14），它是oxo-C14-HSL的结构重排产物，也能诱导[硅藻名称未给出]生长抑制。处理3天后，分析显示有3410个基因因至少一种化合物的作用而差异表达。在用促进生长的C14-HSL处理时，许多参与细胞内信号传导的基因上调。另一方面，暴露于抑制生长的oxo-C14-HSL和TA14会引发脂质代谢向脂肪酸降解增加的转变。此外，oxo-C14-HSL导致细胞周期基因下调，这与该处理中细胞生长停滞一致。综合来看，我们的结果表明，具有高度结构相似性的细菌信号分子在[硅藻名称未给出]中诱导出相反的生理反应。
