Wastewater treatment plant effluents release microbiological pollutants, including the intI1 gene (integrases of class 1 integron), which has been proposed as a target for monitoring anthropogenic pollution in surface waters. This gene correlates with antibiotic resistance genes, making it an important proxy for genetic contamination in aquatic environments. It is currently unclear whether intI1 found in lake water is mainly present due to continuous seeding or if autochthonous bacteria harbor this gene. To better understand the fate and dynamics of class 1 integrons in aquatic systems, we resorted to classical limnological monitoring of intI1 (qPCR) over multiple years in three different size fractions: free‐living bacteria, particle‐attached bacteria, and zooplankton‐attached bacteria. We also conducted experiments to elucidate the impact of grazers on the abundance of intI1. The monitoring of different size fractions of the Lake Maggiore microbial community showed a particle‐bound lifestyle for intI1‐hosting bacteria. Most of these bacteria originated from both a wastewater effluent that discharges into Lake Maggiore and the lake water itself (amplicon sequencing). We hypothesize that these bacteria grow on particles in open waters, making them particularly vulnerable to grazing by large filter feeders such as Daphnia. Therefore, the presence of Daphnia reduced the abundance of intI1 in lake water, whereas this was not true for other grazers such as Rotaria macrura or Poterioochromonas sp. Our study shows that the food web structure and temporal changes in the lake influence the abundance of intI1 and consequently the assessment of anthropogenic pollution.

中文翻译：

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浮游动物放牧减少了湖水中人为污染标记的持久性


废水处理厂废水释放微生物污染物，包括 intI1 基因（1 类整合子整合酶），该基因已被提议作为监测地表水人为污染的目标。该基因与抗生素抗性基因相关，使其成为水生环境中遗传污染的重要代表。目前尚不清楚湖水中发现的intI1是否主要是由于连续播种而存在，还是本地细菌携带该基因。为了更好地了解水生系统中 1 类整合子的命运和动态，我们对 intI1 (qPCR) 进行了多年的经典湖泊学监测，对三种不同大小的部分进行了监测：自由生活的细菌、颗粒附着的细菌和浮游动物附着的细菌。我们还进行了实验来阐明食草动物对 intI1 丰度的影响。对马焦雷湖微生物群落不同大小部分的监测表明，intI1 宿主细菌具有颗粒束缚的生活方式。这些细菌大多数源自排入马焦雷湖的废水和湖水本身（扩增子测序）。我们假设这些细菌在开放水域的颗粒上生长，使它们特别容易被大型滤食动物（例如水蚤）吃草。因此，水蚤的存在降低了湖水中 intI1 的丰度，而对于其他食草动物，如 Rotaria macrura 或 Poterioochromonas sp. 来说，情况并非如此。我们的研究表明，湖泊中的食物网结构和时间变化会影响 intI1 的丰度，从而影响人为污染的评估。