Shanghai Key Lab for Urban Ecological Processes and Eco-Restorations, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China.
Jiangsu Wuxi Environmental Monitoring Center, Jiangsu, China.
mSystems. 2023 Apr 27;8(2):e0099222. doi: 10.1128/msystems.00992-22. Epub 2023 Mar 16.
Cyanobacterial aggregates (CAs) comprised of photosynthetic and phycospheric microorganisms are often the cause of cyanobacterial blooms in eutrophic freshwater lakes. Although phylogenetic diversity in CAs has been extensively studied, much less was understood about the activity status of microorganisms inside CAs and determinants of their activities. In this study, the 16S rRNA gene (rDNA)-based total communities within CAs in Lake Taihu of China were analyzed over a period of 6 months during the bloom season; the 16S rRNA-based active communities during daytime, nighttime, and under anoxic conditions were also profiled. Synchronous turnover of both cyanobacterial and phycospheric communities was observed, suggesting the presence of close interactions. The rRNA/rDNA ratio-based relative activities of individual taxa were predominantly determined by their rDNA-based relative abundances. In particular, high-abundance taxa demonstrated comparatively lower activities, whereas low-abundance taxa were generally more active. In comparison, hydrophysicochemical factors as well as diurnal and redox conditions showed much less impact on relative activities of microbial taxa within CAs. Nonetheless, total and active communities exhibited differences in community assembly processes, the former of which were almost exclusively controlled by homogeneous selection during daytime and under anoxia. Taken together, the results from this study provide novel insights into the relationships among microbial activities, community structure, and environmental conditions and highlight the importance of further exploring the regulatory mechanisms of microbial activities at the community level. Cyanobacterial aggregates are important mediators of biogeochemical cycles in eutrophic lakes during cyanobacterial blooms, yet regulators of microbial activities within them are not well understood. This study revealed rDNA-based abundances strongly affected the relative activities of microbial taxa within aggregates, as well as trade-off effects between microbial abundances and activities. Environmental conditions further improved the levels of relative activities and affected community assembly mechanisms in phycospheric communities. The relationships among microbial activities, abundances, and environmental conditions improve our understanding of the regulatory mechanisms of microbial activities in cyanobacterial aggregates and also provide a novel clue for studying determinants of microbial activities in other ecosystems.
蓝藻聚集体（CAs）由光合和菌胶团微生物组成，通常是富营养化淡水湖中蓝藻水华的成因。尽管已经广泛研究了 CAs 中的系统发育多样性，但对 CAs 内部微生物的活性状态及其活性的决定因素知之甚少。在这项研究中，对中国太湖蓝藻水华季节期间 6 个月内 CAs 中的基于 16S rRNA 基因（rDNA）的总群落进行了分析；还分析了白天、夜间和缺氧条件下基于 16S rRNA 的活性群落。观察到蓝藻和菌胶团群落的同步周转，表明存在密切的相互作用。个体分类单元的 rRNA/rDNA 比值相对活性主要由其 rDNA 相对丰度决定。特别是，高丰度分类单元表现出相对较低的活性，而低丰度分类单元通常更活跃。相比之下，水理化因素以及昼夜和氧化还原条件对 CAs 内微生物分类单元的相对活性影响较小。尽管如此，总群落和活性群落表现出不同的群落组装过程，前者在白天和缺氧条件下几乎完全由同型选择控制。总的来说，这项研究的结果提供了关于微生物活性、群落结构和环境条件之间关系的新见解，并强调了进一步探索社区水平微生物活性调节机制的重要性。在蓝藻水华期间，蓝藻聚集体是富营养化湖泊中生物地球化学循环的重要介体，但其中微生物活性的调节剂尚不清楚。本研究揭示了 rDNA 丰度强烈影响了聚集体内部微生物分类单元的相对活性，以及微生物丰度和活性之间的权衡效应。环境条件进一步提高了相对活性水平，并影响了菌胶团群落的群落组装机制。微生物活性、丰度和环境条件之间的关系提高了我们对蓝藻聚集体中微生物活性调节机制的理解，也为研究其他生态系统中微生物活性的决定因素提供了新的线索。
