活性污泥微生物泛化种和特化种的构建机制与进化速率

【背景】活性污泥中细菌和微型真核生物在污水处理中扮演了重要角色,然而目前对其泛化种和特化种的研究尚不充分。【目的】分析活性污泥中微生物泛化种和特化种的结构与环境因子相关性,研究其群落构建机制、进化速率和多样化潜力。【方法】以中国东南沿海某地污水厂中活性污泥微生物群落为研究对象,利用扩增子测序技术和多元统计技术分析了泛化种和特化种的结构特征,并通过基于系统发育分箱的零模型(infer community assembly mechanisms by phylogenetic-bin-based null model analysis,iCAMP)和二分成种与灭绝(binary-state speciation and extinction,BiSSE)模型分别研究了其构建机制及进化速率。【结果】细菌泛化种和特化种与电导率、NH_(4)^(+)-N和NO_(2)^(–)-N显著相关,而总氮(total nitrogen,TN)是影响微型真核生物泛化种和特化种的关键因子。此外,电导率和NO_(2)^(–)-N对微型真核生物特化种也有着重要影响。以漂变和扩散限制为主的随机作用是影响上述群落的主要生态学机制(泛化种大于特化种),并且对微型真核生物的影响更强。相较于微型真核生物,细菌具有较高的成种速率、多样化潜力及较低的灭绝速率;相较于泛化种,特化种具有较高的成种速率、灭绝速率和多样化潜力。【结论】NH_(4)^(+)-N、NO_(2)^(–)-N和电导率是影响细菌泛化种、细菌特化种和微型真核生物特化种的重要环境因子。泛化种和特化种主要受漂变和扩散限制的影响,其成种速率存在差异。

Seasonal hydrological dynamics govern lifestyle preference of aquatic antibiotic resistome

Antibiotic resistance genes(ARGs)are a well-known environmental concern.Yet,limited knowledge exists on the fate and transport of ARGs in deep freshwater reservoirs experiencing seasonal hydrological changes,especially in the context of particle-attached(PA)and free-living(FL)lifestyles.Here,the ARG profiles were examined using high-throughput quantitative PCR in PA and FL lifestyles during four seasons representing two hydrological phenomena(vertical mixing and thermal stratification)in the Shuikou Reservoir(SR),Southern China.The results indicated that seasonal hydrological dynamics were critical for influencing the ARGs in PA and FL and the transition of ARGs between the two lifestyles.ARG profiles both in PA and FL were likely to be shaped by horizontal gene transfer.However,they exhibited distinct responses to the physicochemical(e.g.,nutrients and dissolved oxygen)changes under seasonal hydrological dynamics.The particle-association niche(PAN)index revealed 94 non-conservative ARGs(i.e.,no preferences for PA and FL)and 23 and 16 conservative ARGs preferring PA and FL lifestyles,respectively.A sharp decline in conservative ARGs under stratified hydrologic suggested seasonal influence on the ARGs transition between PA and FL lifestyles.Remarkably,the conservative ARGs(in PA or FL lifestyle)were more closely related to bacterial OTUs in their preferred lifestyle than their counterparts,indicating lifestyle-dependent ARG enrichment.Altogether,these findings enhanced our understanding of the ARG lifestyles and the role of seasonal hydrological changes in governing the ARG transition between the lifestyles in a typical deep freshwater ecosystem.