Institute of International Rivers and Eco-Security, Yunnan University, Kunming 650500, China.
Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Kunming 650500, China.
FEMS Microbiol Ecol. 2020 Aug 1;96(8). doi: 10.1093/femsec/fiaa132.
Terrestrial microbial communities may take advantage of running waters and runoff to enter rivers and mix with aquatic microorganisms. However, the environmental factors governing the interchange of the microbial community within a watercourse and its surrounding environment and the composition of the resulting community are often underestimated. The present study investigated the effect of flow rate on the mixing of water, soil, sediment and biofilm at four sites along the Lancang River and one branch of the river in winter and summer and, in turn, the resultant changes in the microbial community within each habitat. 16S rRNA gene-based Illumina high-throughput sequencing illustrated that bacterial communities were apparently distinct among biofilm, water, soil and sediment. Biofilms had the lowest richness, Shannon diversity and evenness indices compared with other habitats, and those three indices in all habitats increased significantly from winter to summer. SourceTracker analysis showed a significant coalescence between the bacterial communities of sediment, water and biofilm samples at lower flow rates. Additionally, the proportion of Betaproteobacteria in sediment and biofilms increased with a decrease in flow rate, suggesting the flow rate had a strong impact on microbial community composition and exchange among aquatic habitats. These results were further confirmed by a Mantel test and linear regression analysis. Microbial communities in all samples exhibited a significant but very weak distance-decay relationship (r = 0.093, P = 0.024). Turbidity played a much more important role on water bacterial community structure in summer (i.e. rainy season) (BIOENV, r = 0.92). Together, these results suggest that dispersal is an important factor affecting bacterial community structure in this system.
陆地微生物群落可能会利用流水和径流入河，并与水生微生物混合。然而，控制水道内微生物群落与其周围环境交换以及形成的群落组成的环境因素通常被低估。本研究调查了流速对澜沧江干流和一条支流冬季和夏季四个地点的水、土壤、沉积物和生物膜混合的影响，以及由此导致的每个生境中微生物群落的变化。基于 16S rRNA 基因的 Illumina 高通量测序表明，生物膜、水、土壤和沉积物中的细菌群落明显不同。与其他栖息地相比，生物膜的丰富度、香农多样性和均匀度指数最低，所有栖息地的这三个指数从冬季到夏季均显著增加。SourceTracker 分析表明，在较低流速下，沉积物、水和生物膜样本的细菌群落明显聚集。此外，随着流速的降低，沉积物和生物膜中β变形菌的比例增加，表明流速对微生物群落组成和水生栖息地之间的交换有很强的影响。这一结果进一步通过 Mantel 检验和线性回归分析得到证实。所有样本中的微生物群落都表现出显著但非常微弱的距离衰减关系（r=0.093，P=0.024）。在夏季（即雨季），浊度对水细菌群落结构的影响要大得多（即 BIOENV，r=0.92）。总之，这些结果表明，扩散是影响该系统细菌群落结构的一个重要因素。
