Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.
Cooperative Institute for Great Lakes Research, School of Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA.
Microb Ecol. 2021 Jan;81(1):1-13. doi: 10.1007/s00248-020-01539-0. Epub 2020 Jul 3.
Bacteria play a key role in freshwater biogeochemical cycling as well as water safety, but short-term trends in freshwater bacterial community composition and dynamics are not yet well characterized. We sampled four public beaches in southern Ontario, Canada; in June, July, and August (2016) over a 24-h (diel) cycle at 2-h intervals. Using high-throughput sequencing of 16S rRNA gene, we found substantial bi-hourly and day/night variation in the bacterial communities with considerable fluctuation in the relative abundance of Actinobacteria and Proteobacteria phyla. Moreover, relative abundance of Enterobacteriaceae (associated with potential health risk) was significantly high at night in some dial cycles. Diversity was significantly high at night across most of the diel sampling events. qPCR assays showed a substantial bi-hourly variation of Escherichia coli levels with a significant high level of E. coli at night hours in comparison with day hours and the lowest levels at noon and during the afternoon hours. Taken together, these findings highlighted a considerable short-term temporal variation of bacterial communities which helps better understanding of freshwater bacterial dynamics and their ecology. E. coli monitoring showed that multiple samples in different hours will provide more accurate picture of freshwater safety and human health risk. Graphical abstract.
细菌在淡水生物地球化学循环以及水安全中起着关键作用，但目前还不太清楚淡水细菌群落组成和动态的短期趋势。我们在加拿大安大略省南部的四个公共海滩进行了采样；在 2016 年 6 月、7 月和 8 月（24 小时周期）每隔两小时进行一次采样。我们使用 16S rRNA 基因的高通量测序发现，细菌群落存在显著的每两小时和昼夜变化，放线菌和变形菌门的相对丰度波动较大。此外，某些昼夜循环中肠杆菌科（与潜在健康风险相关）的相对丰度在夜间显著较高。在大多数昼夜采样事件中，多样性在夜间显著较高。qPCR 检测显示，大肠杆菌水平存在显著的每两小时变化，与白天相比，夜间大肠杆菌水平显著较高，而中午和下午大肠杆菌水平最低。总的来说，这些发现突出了细菌群落的相当大的短期时间变化，有助于更好地了解淡水细菌动态及其生态学。大肠杆菌监测表明，不同时间的多个样本将更准确地反映淡水安全和人类健康风险。图表摘要。
