淡水湖泊受到有害水华的威胁,这些水华的特征是蓝细菌聚集体(CA),通常与蓝细菌释放的细胞外多糖聚集在一起,形成了植物圈。在这些CA中,细菌和蓝细菌之间可能存在相互关系,其中细菌产物补充蓝细菌的生长,和蓝细菌分泌物,反过来,作为细菌的底物,从而增强每个成分的稳定性。然而,关于蓝细菌和它们在CA中附着的细菌之间的确切相互作用知之甚少。因此,在这项研究中,我们从太湖采集了26个CA样本,2015年3月至2016年2月中国的大型淡水湖。然后我们对16SrRNA基因的V4区域和完整的宏基因组进行了测序,产生610Mb的16SrRNA基因数据和198.98Gb的高质量宏基因组数据。我们观察到,在采样时间内,两个蓝藻属(微囊藻和Dolichospermum)交替主导CA,而附着于不同蓝藻属的特定细菌属主导CA。更具体地说,当水温较低且总氮较高时,Dolichospermum在CA中占主导地位,而当水温高,总氮低时,微囊藻在CA中占主导地位。此外,我们发现特定的细菌属附着于不同的蓝细菌属占主导地位的CA。通过构建生态网络检测蓝藻-细菌相关对Dolichospermum-Burkholderia和微囊藻-hyphomonas。发现CA中的细菌群落与蓝细菌群落(Mantel\sr=0.76,P=0.001)的相关性高于与环境因素(Mantel\sr=0.27,P=0.017)的相关性。构建了蓝细菌及其附着细菌之间潜在的协同依赖氮循环途径,表明他们的功能联系。总的来说,这些结果表明,互惠的关系,的确,在分类学和基因水平上都存在于CA中的蓝细菌和细菌之间,通过干预策略破坏细菌-蓝细菌关系和共途径,提供可能导致水华控制的生物学线索。
Freshwater lakes are threatened by harmful blooms characterized by Cyanobacterial Aggregates (CAs) that are normally aggregated with extracellular polysaccharides released by cyanobacteria to form a phycosphere. It is possible that mutualistic relationships exist between bacteria and cyanobacteria in these CAs wherein bacterial products supplement cyanobacterial growth, and cyanobacterial exudates, in turn, serve as substrates for bacteria, thus augmenting the stability of each constituent. However, little is known about the exact interaction between cyanobacteria and their attached bacteria in CAs. Therefore, in this study, we collected 26 CA samples from Lake Taihu, a large freshwater lake in
China from March of 2015 to February of 2016. We then sequenced both the V4 regions of 16S rRNA genes and full metagenomes, resulting in 610 Mb of 16S rRNA gene data and 198.98 Gb of high-quality metagenomic data. We observed that two cyanobacteria genera (Microcystis and
Dolichospermum) alternately dominated CAs along the sampling time and specific bacterial genera attached to different cyanobacteria genera dominated CAs. More specifically,
Dolichospermum dominates CAs when water temperature is low and total nitrogen is high, while Microcystis dominates CAs when water temperature is high and total nitrogen is low. Moreover, we found specific bacterial genera attached to different cyanobacteria genera dominated CAs. The cyanobacteria-bacteria related pairs
Dolichospermum-Burkholderia and Microcystis-Hyphomonas were detected by ecological networks construction. Bacterial communities in CAs were found to be more correlated with the cyanobacterial community (Mantel\'s r = 0.76, P = 0.001) than with environmental factors (Mantel\'s r = 0.27, P = 0.017). A potential codependent nitrogen-cycling pathway between cyanobacteria and their attached bacteria was constructed, indicating their functional link. Overall, these results demonstrated that mutualistic relationships do, indeed, exist between cyanobacteria and bacteria in CAs at both taxonomic and gene levels, providing biological clues potentially leading to the control of blooms by interventional strategies to disrupt bacteria-cyanobacteria relationships and co-pathways.