In the rhizosphere, plant root exudates can mediate the toxicity of antibiotics on microorganisms, yet the mechanisms are poorly understood. To simulate the antibiotic contamination of global rivers and lakes, the current study investigated the effects of two antibiotics (ofloxacin at 8.69 × 104 ng L-1 and tetracycline at 8.62 × 104 ng L-1) and their binary combination (8.24 × 104 ng L-1 ofloxacin and 7.11 × 104 ng L-1 tetracycline) on bacterial communities in micro-polluted constructed wetlands with and without artificial root exudates. The two antibiotics had no significant effects on the removal of excess carbon and nitrogen from the microcosms treated with and without exudates. Furthermore, with regard to bacterial community structure, antibiotic exposure increased the bacterial richness of bulk and exudate treated microcosms (P < 0.05). However, a significant increase (P < 0.05) in bacterial diversity elicited by ofloxacin and antibiotic mixture exposure was only observed in microcosms with exudates. In exudate treated microcosms, ofloxacin promoted the relative abundance of Arthrobacter spp., which are ofloxacin-resistant bacterial species, which significantly varied from what was observed in microcosms free of exudates. Moreover, tetracycline, ofloxacin and their combination all significantly increased the relative abundance of nitrogen cycling bacteria Rhizobacter spp. and Rhizobium spp., and decreased the relative abundance of antibiotic-resistant bacteria Pseudomonas spp. Simultaneously, with regard to bacterial community functions, the functional profiles (Kyoto Encyclopedia of Genes and Genomes) showed that the pathways of amino acid and carbohydrate metabolism were enhanced by antibiotics in microcosms with exudates. The findings illustrate that antibiotics not only alter the bacterial structure and composition but also change their functional properties in constructed wetlands, and these interruption effects could be affected by root exudates of plants, which may further reveal the ecological implication of plants in constructed wetlands.

中文翻译：

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抗生素对人工根系分泌物处理过的人工湿地中微生物群落结构和微生物功能的影响。

在根际中，植物根系分泌物可以介导抗生素对微生物的毒性，但其机理尚不清楚。为了模拟全球河流和湖泊的抗生素污染，当前的研究调查了两种抗生素（氟沙星浓度为8.69×104 ng L-1和四环素浓度为8.62×104 ng L-1）及其二元组合（8.24×104 ng）的影响。 L-1氧氟沙星和7.11×104 ng L-1四环素）在有或没有人工根系分泌物的微污染人工湿地上的细菌群落上。两种抗生素对使用和不使用渗出液处理的微观世界中多余的碳和氮的去除均无明显影响。此外，就细菌群落结构而言，抗生素暴露增加了散装和渗出液处理过的微生物的细菌丰富度（P <0.05）。然而，氧氟沙星和抗生素混合物暴露引起的细菌多样性显着增加（P <0.05），仅在渗出液的微观世界中观察到。在经渗出液处理的微观世界中，氧氟沙星提高了对关节杆菌的耐药性，这是耐氧氟沙星的细菌种类，与无渗出液的微观世界中观察到的细菌相比有显着差异。此外，四环素，氧氟沙星及其组合都显着增加了氮循环细菌根瘤菌的相对丰度。和根瘤菌属，并降低了抗生素抗性细菌假单胞菌的相对丰度。同时，关于细菌群落功能，功能概况（《基因和基因组京都百科全书》）显示，在渗出液微观世界中，抗生素可增强氨基酸和碳水化合物的代谢途径。这些发现表明，抗生素不仅会改变人工湿地中的细菌结构和组成，而且会改变其功能特性，这些干扰作用可能受到植物根系分泌物的影响，这可能进一步揭示了人工湿地中植物的生态学意义。