Recognition, signalling and response of the diatom Fragilariopsis to epibiotic bacterial colonization.

硅藻脆弱菌对表生细菌定植的识别、信号传导和反应。

• 批准号: 442925794
• 负责人: Professor Dr. Tilmann Harder
• 金额: --
• 依托单位: Arbeitsgruppe Neurobiochemistry
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/442925794?language=en
• 关键词: Recognition; signalling; response; diatom; Fragilariopsis

The diatom Fragilariopsis dominates phytoplankton in the Southern Ocean and plays a central role in the significant (15% of global) primary productivity of Antarctic regions. Marine primary production is fuelled by spatially close interactions between microalgae and bacteria and driven by their reciprocal needs for essential trace elements, micro- and macro-nutrients. Several recent microbiome studies of diverse phytoplankton species suggest that they harbour unique microbiomes, which are consistent and specific within phytoplankton species and across temporal scales. Yet, the mechanistic processes causing these associations at different levels of specialization are poorly understood.The main hypothesis addressed in this proposal postulates that Fragilariopsis relies on, or employs comparable recognition and transduction strategies in response to environmental bacteria as animals and plants, despite their phylogenetic distance to the diatom. Thus, in theory this analogy allows a cross-disciplinary transfer of methodology from well investigated immunity and microbiome science in animals and plants to a phytoplankton species.The concept of active recognition, selection and filtering processes, which supposedly steer the assembly of Fragilariopsis-associated microbiomes, is well understood in the context of immunity in multicellular organisms, even in multicellular marine macroalgae, but not in diatoms. Such responses are triggered via receptor-mediated recognition of bacterial elicitors and mediated by well-investigated signaling cascades (e.g. via nitric oxide (NO)). As a consequence, this leads to the upregulation of a variety of quantifiable stress markers, such as intracellular reactive oxygen species or a shift of the glutathione to glutathione-disulfide ratio. Partially, these stress markers have been verified in microalgae and first evidence of NO signaling and NO synthase-like gene sequences in marine diatoms is emerging. This proposal thus addresses pertinent DFG SPP questions, such as the need of “improved understanding of polar processes and mechanisms'' and the “response [of SO organisms] to environmental change”. Specifically, we will isolate, culture and identify various bacteria from Fragilariopsis microbiomes. In parallel, different Fragilariopsis ecotypes are axenified. In co-culture assays, we will employ known and well established chemical and molecular tools to characterize and quantify intra- and extracellular responses of Fragilariopsis to bacteria and bacterial molecular elicitors, such as bacterial lipopolysaccharides.The short term goal of this proposal is to corroborate an active response of Fragilariopsis to bacteria or bacterial signaling molecules. The long-term goal of this work is to analyse the holobiont assembly and challenge the recognition process by experimentally adjusting future SO climate regimes to understand the susceptibility of the Fragilariopsis holobiont to predicted climate change scenarios.

硅藻Fragilariopsis占主导地位的浮游植物在南大洋，并在南极地区的显着（全球的15%）初级生产力的核心作用。微藻和细菌在空间上的密切相互作用以及它们对基本微量元素、微量营养素和大量营养素的相互需求推动了海洋初级生产。最近对不同浮游植物物种的几项微生物组研究表明，它们拥有独特的微生物组，这些微生物组在浮游植物物种内和跨时间尺度上是一致和特异的。然而，机械过程导致这些协会在不同层次的专业化知之甚少。在这个建议中提出的主要假设假设假定，Fragilariopsis依赖于，或采用类似的识别和转导策略，在响应环境细菌的动物和植物，尽管他们的系统发育距离硅藻。因此，从理论上讲，这种类比允许从动物和植物的免疫和微生物组科学到浮游植物物种的跨学科方法转移。主动识别，选择和过滤过程的概念，据说引导Fragilariopsis相关微生物组的组装，在多细胞生物的免疫背景下得到很好的理解，即使在多细胞海洋大型藻类中，但不在硅藻中。这种反应是通过受体介导的细菌激发子识别触发的，并通过充分研究的信号级联（例如，通过一氧化氮（NO））介导。因此，这导致各种可量化的应激标志物的上调，例如细胞内活性氧或谷胱甘肽与谷胱甘肽-二硫化物比率的变化。部分地，这些应激标记物已在微藻中得到验证，并且海洋硅藻中的NO信号传导和NO脱氢酶样基因序列的第一个证据正在出现。因此，这一建议解决了相关的DFG SPP问题，如需要“提高对极地过程和机制的理解”和“对环境变化的反应”。具体来说，我们将分离，培养和鉴定各种细菌从Fragilariopsis微生物组。平行地，使不同的拟脆杆藻生态型无菌化。在共培养试验中，我们将采用已知的和成熟的化学和分子工具来表征和定量脆杆藻对细菌和细菌分子激发子（如细菌脂多糖）的细胞内和细胞外反应，本提案的短期目标是证实脆杆藻对细菌或细菌信号分子的主动反应。这项工作的长期目标是分析的holobiont大会和挑战的识别过程中，通过实验调整未来SO气候制度，以了解脆弱的holobiont预测的气候变化情景的敏感性。