The diazotrophic community in microbial mats growing along the shore of the North Sea barrier island Schiermonnikoog (The Netherlands) was studied using microscopy, lipid biomarkers, stable carbon (δ¹³C_TOC) and nitrogen (δ¹⁵N) isotopes as well as by constructing and analyzing 16S rRNA gene libraries. Depending on their position on the littoral gradient, two types of mats were identified, which showed distinct differences regarding the structure, development and composition of the microbial community. Intertidal microbial mats showed a low species diversity with filamentous non‐heterocystous Cyanobacteria providing the main mat structure. In contrast, supratidal microbial mats showed a distinct vertical zonation and a high degree of species diversity. Morphotypes of non‐heterocystous Cyanobacteria were recognized as the main structural component in these mats. In addition, unicellular Cyanobacteria were frequently observed, whereas filamentous heterocystous Cyanobacteria occurred only in low numbers. Besides the apparent visual dominance of cyanobacterial morphotpyes, 16S rRNA gene libraries indicated that both microbial mat types also included members of the Proteobacteria and the Cytophaga–Flavobacterium–Bacteroides group as well as diatoms. Bulk δ¹⁵N isotopes of the microbial mats ranged from +6.1‰ in the lower intertidal to −1.2‰ in the supratidal zone, indicating a shift from predominantly nitrate utilization to nitrogen fixation along the littoral gradient. This conclusion was supported by the presence of heterocyst glycolipids, representing lipid biomarkers for nitrogen‐fixing heterocystous Cyanobacteria, in supratidal but not in intertidal microbial mats. The availability of combined nitrogen species might thus be a key factor in controlling and regulating the distribution of the diazotrophic microbial community of Schiermonnikoog.

中文翻译：

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北海南部沿海微生物垫的重氮营养微生物群落。

使用显微镜，脂质生物标志物，稳定碳（δ微生物垫沿着北海屏障Schiermonnikoog岛（荷兰）的岸边越来越多的固氮社会研究¹³ Ç _TOC）和氮（δ ¹⁵N）同位素以及通过构建和分析16S rRNA基因文库。根据它们在沿海梯度上的位置，确定了两种类型的垫子，它们在微生物群落的结构，发育和组成方面显示出明显的差异。潮间带微生物垫显示出较低的物种多样性，其中主要的垫结构是丝状非异型蓝藻蓝细菌。相比之下，上方的微生物垫显示出明显的垂直分区和高度的物种多样性。非异型蓝藻的形态被认为是这些垫子的主要结构成分。此外，经常观察到单细胞蓝细菌，而丝状异囊蓝细菌仅以少量出现。除了蓝藻吗啉的明显视觉优势外，16S rRNA基因文库表明，两种微生物垫类型还包括变形杆菌属和细胞吞噬素-黄杆菌-拟杆菌属以及硅藻。体积δ微生物垫层的¹⁵ N同位素范围从潮间带下部的+ 6.1‰到潮间带的-1.2‰，表明沿沿海梯度从主要利用硝酸盐转移到固氮。该结论得到潮间微生物垫中不存在异种糖脂的支持，异种糖脂代表固定氮的异囊蓝藻的脂质生物标记。因此，结合氮物种的可用性可能是控制和调节Schiermonnikoog重氮营养微生物群落分布的关键因素。