Schallenberg Lena A, Pearman John K, Burns Carolyn W, Wood Susanna A
Department of Zoology, University of Otago, Dunedin, New Zealand.
Coastal and Freshwater Group, Cawthron Institute, Nelson, New Zealand.
Front Microbiol. 2021 Nov 12;12:757929. doi: 10.3389/fmicb.2021.757929. eCollection 2021.
Picocyanobacteria (Pcy) are important yet understudied components of lake foodwebs. While phylogenetic studies of isolated strains reveal a high diversity of freshwater genotypes, little is known about abiotic drivers associated with Pcy in different lakes. Due to methodological limitations, most previous studies assess potential drivers using total cell abundances as a response, with often conflicting and inconsistent results. In the present study, we explored how picocyanobacterial communities respond to environmental change using a combination of epifluorescence microscopy and community data determined using 16S rRNA gene metabarcoding. Temporal shifts in picocyanobacterial abundance, diversity and community dynamics were assessed in relation to potential environmental drivers in five contrasting lakes over 1year. Cell abundances alone were not consistently related to environmental variables across lakes. However, the addition of metabarcoding data revealed diverse picocyanobacterial communities that differed significantly between lakes, driven by environmental variables related to trophic state. Within each lake, communities were temporally dynamic and certain amplicon sequence variants (ASVs) were strongly associated with specific environmental drivers. Rapid shifts in community structure and composition were often related to environmental changes, indicating that lacustrine Pcy can persist at high abundances through collective community adaptation. These results demonstrate that a combination of microscopy and metabarcoding enables an in-depth characterisation of picocyanobacterial communities and reveals strain-specific drivers. We recommend that future studies cease referring to picocyanobacterial as one functional group and take strain specific variability into consideration.
蓝细菌是湖泊食物网中重要但研究不足的组成部分。虽然对分离菌株的系统发育研究揭示了淡水基因型的高度多样性，但对于不同湖泊中与蓝细菌相关的非生物驱动因素知之甚少。由于方法上的局限性，大多数先前的研究以总细胞丰度作为响应来评估潜在驱动因素，结果往往相互矛盾且不一致。在本研究中，我们结合落射荧光显微镜和使用16S rRNA基因宏条形码测定的群落数据，探索了蓝细菌群落如何响应环境变化。在1年的时间里，我们评估了五个不同湖泊中蓝细菌丰度、多样性和群落动态的时间变化与潜在环境驱动因素的关系。仅细胞丰度在不同湖泊中与环境变量的关系并不一致。然而，宏条形码数据的加入揭示了不同湖泊中差异显著的蓝细菌群落，这些群落由与营养状态相关的环境变量驱动。在每个湖泊中，群落随时间动态变化，某些扩增子序列变体（ASVs）与特定的环境驱动因素密切相关。群落结构和组成的快速变化通常与环境变化有关，这表明湖泊中的蓝细菌可以通过集体群落适应在高丰度下持续存在。这些结果表明，显微镜和宏条形码技术的结合能够深入表征蓝细菌群落，并揭示菌株特异性驱动因素。我们建议未来的研究不要再将蓝细菌视为一个功能组，而是要考虑菌株特异性变异性。
