Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China.
Sci Total Environ. 2020 Oct 20;740:140010. doi: 10.1016/j.scitotenv.2020.140010. Epub 2020 Jun 6.
Both the planktonic bacterial community (PBC) and benthic bacterial community (BBC) are important for biogeochemical processes in freshwater lakes. Despite their ecological significance, little is known about their seasonal co-occurrence patterns and the ecological processes that drive them. In this study, we aimed to investigate the ecological associations among bacterial taxa and assembly processes of PBC and BBC in different seasons. We used 16S rRNA gene high-throughput sequencing of a total of 150 water and sediment samples collected from multiple lakes distributed in an urban region of China during winter and summer. Our results revealed that PBC showed stronger seasonal variations in co-occurrence patterns than BBC, suggesting that BBC had greater temporal stability than PBC. Winter PBC network was characterized by higher connectivity and complexity, and thereby the formation of a highly stable community structure; whereas lower connectivity arising from the presence of fewer predicted keystone taxa (hubs and connectors in a network) was destabilizing to summer PBC network. In addition, the phylum Firmicutes identified as a putative keystone taxon of PBC in both seasons played a non-negligible role in maintaining network structure which may result from strong functional associations with other bacterioplankton. Temperature and pH were the best explanatory factors predicting the seasonal co-occurrence patterns of PBC and BBC, respectively. Normalized stochasticity ratio based on null-model analysis indicated that deterministic processes overwhelmed stochastic processes in governing the assembly of PBC and BBC in both seasons. However, we observed a greater influence of ecological stochasticity on BBC assembly than PBC assembly in both seasons. Taken together, these findings provide insights into understanding the impacts of habitat heterogeneity and seasonal variability on microbial assemblage patterns in lake ecosystems.
浮游细菌群落（PBC）和底栖细菌群落（BBC）对于淡水湖泊的生物地球化学过程都很重要。尽管它们具有生态意义，但人们对它们的季节性共存模式以及驱动它们的生态过程知之甚少。在这项研究中，我们旨在调查不同季节 PBC 和 BBC 中细菌分类群之间的生态关联和组装过程。我们使用了 16S rRNA 基因高通量测序技术，对来自中国一个城市地区的多个湖泊在冬季和夏季采集的总共 150 个水和沉积物样本进行了分析。我们的结果表明，PBC 的共存模式具有更强的季节性变化，而 BBC 的季节性变化较小，这表明 BBC 比 PBC 具有更大的时间稳定性。冬季 PBC 网络的特点是连接性和复杂性较高，从而形成了高度稳定的群落结构；而夏季由于预测的关键类群（网络中的枢纽和连接器）较少，连接性降低，从而使 PBC 网络不稳定。此外，在两个季节中，被确定为 PBC 假定关键类群的厚壁菌门在 PBC 网络中发挥了不可忽视的作用，这可能是由于与其他细菌浮游生物之间存在强烈的功能关联。温度和 pH 是分别预测 PBC 和 BBC 季节性共存模式的最佳解释因素。基于 null 模型分析的归一化随机比表明，在两个季节中，确定性过程在控制 PBC 和 BBC 的组装方面占主导地位，而随机过程的影响较小。然而，我们观察到生态随机性对 BBC 组装的影响大于 PBC 组装。总的来说，这些发现为理解栖息地异质性和季节性变化对湖泊生态系统中微生物组合模式的影响提供了新的认识。
