Søchting Ulrik, Friedl Thomas, Moestrup Øjvind, Grewe Felix, Sun Yukun, Çakır Yağmur Tarhana, Ganzera Markus, Glaser Karin, Heesch Svenja, Hammerle Fabian, Nimptsch Daniel, Olberg Birgit, Karsten Ulf
Section Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Department Experimental Phycology and Culture Collection of Algae (EPSAG), Albrecht-von-Haller-Institute for Plant Sciences, Georg August University, Göttingen, Germany.
Front Microbiol. 2025 Jul 23;16:1633308. doi: 10.3389/fmicb.2025.1633308. eCollection 2025.
A filamentous green alga forming significant biomass on twigs and needles was observed to have increased invasively in Denmark in recent decades. It was particularly abundant in coniferous plantations in western parts of Denmark that experience the highest modelled concentration of atmospheric nitrogen deposition. However, its species identity and taxonomy remained unknown.
Selected algal samples from various substrates were analyzed for their ribosomal DNA sequences, metagenomic, and biochemical compounds [polyols and mycosporine-like amino acids (MAAs)].
Phylogenetic analyses revealed the alga's position within the Trebouxiophyceae (Chlorophyta), forming an independent lineage within . Though it was associated with various other Trebouxiophyceae species, the metagenome showed exceptionally high coverage of the contigs, proving its predominance, consistent with the amplicon-based approach. The low molecular weight carbohydrates, arabitol, erythritol, and trehalose - with erythritol displaying the highest concentrations-were recovered. The presence of erythritol provided chemotaxonomic support for the classification in . Additionally, a unique UV-absorbing mycosporine amino acid (MAA), likely new for the Trebouxiophyceae, was found. The species is described here as , and the observed morphological features leave no doubt that it has been recorded from Denmark more than a 100 years ago. Morphological features are shared with its closer relatives, such as the presence of a ring of particles surrounding the nucleus and the formation of two-celled units.
The presence of low molecular weight carbohydrates and the unique MAA in well explain the biochemical basis for its aeroterrestrial lifestyle, as these organic compounds protect against desiccation and UV-radiation, respectively. Even though the genotype of has also been found in inconspicuous biofilms devoid of filamentous stages on various substrates with presumably low ammonia deposition, the very invasive colonization in recent decades in western Denmark is assumed to be due to ammonia deposition. Consequently, is suggested to be a potential biological indicator of air borne nitrogen deposition. A possible connection between filamentous growth and nitrogen accumulation needs further investigation, including culture experiments.
近几十年来，在丹麦观察到一种丝状绿藻在细枝和针叶上形成大量生物量，并呈入侵性增长。在丹麦西部针叶人工林中这种藻类尤为丰富，该地区模拟的大气氮沉降浓度最高。然而，其物种身份和分类地位仍不清楚。
对从各种基质上选取的藻类样本进行核糖体DNA序列、宏基因组和生化化合物[多元醇和类菌孢素氨基酸（MAAs）]分析。
系统发育分析揭示了该藻类在绿藻门（Chlorophyta）中的位置，属于绿藻纲（Trebouxiophyceae），在 内形成一个独立的谱系。尽管它与其他各种绿藻纲物种相关，但宏基因组显示 重叠群的覆盖率极高，证明了其优势地位，这与基于扩增子的方法一致。回收了低分子量碳水化合物、阿拉伯糖醇、赤藓糖醇和海藻糖，其中赤藓糖醇浓度最高。赤藓糖醇的存在为其在 中的分类提供了化学分类学支持。此外，还发现了一种独特的吸收紫外线的类菌孢素氨基酸（MAA），可能是绿藻纲中的新物质。这里将该物种描述为 ，观察到的形态特征毫无疑问地表明它在100多年前就已在丹麦被记录。其形态特征与其近亲相似，如细胞核周围存在颗粒环以及形成双细胞单位。
中低分子量碳水化合物和独特MAA的存在很好地解释了其气生陆地生活方式的生化基础，因为这些有机化合物分别能防止脱水和抵御紫外线辐射。尽管在氨沉降可能较低的各种基质上，在没有丝状阶段的不显眼生物膜中也发现了 的基因型，但近几十年来在丹麦西部的这种极具入侵性的定殖被认为是由于氨沉降。因此， 被认为是空气传播氮沉降的潜在生物指标。丝状生长与氮积累之间的可能联系需要进一步研究，包括培养实验。
