This study investigated the influences of three frequently detected antibiotics in surface waters, ciprofloxacin, tetracycline and sulfamethoxazole, on the growth, photosynthetic activity, nitrogen-fixing capacity and proteomic expression profiles of Nostoc sp. PCC 7120, through a 15-day exposure test at environmentally relevant exposure doses of 50–200 ng/L. Cyanobacterial growth was stimulated by 100 ng/L and 200 ng/L of ciprofloxacin and sulfamethoxazole as well as 50–200 ng/L of tetracycline. The nitrogenase synthesis ability in each cyanobacterial cell was stimulated by 50–200 ng/L of ciprofloxacin while inhibited by 100 ng/L and 200 ng/L of tetracycline and sulfamethoxazole. At the exposure dose of 100 ng/L for each antibiotic, the variation of total nitrogen in the culture medium indicated that the nitrogen-fixing capacity of Nostoc sp. was determined by total nitrogenase concentration calculated by cell density × nitrogenase synthesis ability. Therefore, ciprofloxacin enhanced nitrogen fixation through the stimulation of both cyanobacterial growth and nitrogenase synthesis, while tetracycline and sulfamethoxazole enhanced nitrogen fixation merely through growth stimulation. At the exposure dose of 100 ng/L, only two downregulated proteins, a phosphonate ABC transporter and a methionine aminopeptidase, as well as one upregulated protein, the phenylalanine-tRNA ligase alpha subunit, were commonly shared by three antibiotic-treated groups. Ciprofloxacin upregulated proteins related to nitrogen fixation, carbon catabolism and biosynthesis, but downregulated photosynthesis-related proteins. In contrast, tetracycline and sulfamethoxazole increased the photosynthetic activity of Nostoc sp. through upregulating photosynthesis-related proteins, but downregulated proteins related to nitrogen fixation, carbon catabolism and biosynthesis. The resistance of Nostoc sp. PCC 7120 to three target antibiotics were related with the responses of RNA synthesis regulatory proteins. Stimulation of cyanobacterial nitrogen fixation by antibiotic contaminants could aggravate eutrophication in aquatic environments.

本研究调查了地表水中常见的三种抗生素环丙沙星、四环素和磺胺甲恶唑对Nostoc生长、光合活性、固氮能力和蛋白质组表达谱的影响。sp. PCC 7120，通过 50–200 ng/L 的环境相关暴露剂量下的 15 天暴露测试。100 ng/L 和 200 ng/L 的环丙沙星和磺胺甲恶唑以及 50-200 ng/L 的四环素可刺激蓝细菌的生长。每个蓝藻细胞的固氮酶合成能力受到 50-200 ng/L 环丙沙星的刺激，而被 100 ng/L 和 200 ng/L 的四环素和磺胺甲恶唑抑制。在每种抗生素的暴露剂量为 100 ng/L 时，培养基中总氮的变化表明Nostoc的固氮能力sp. 由细胞密度×固氮酶合成能力计算的总固氮酶浓度确定。因此，环丙沙星通过刺激蓝藻生长和固氮酶合成增强固氮，而四环素和磺胺甲恶唑仅通过刺激生长增强固氮。在 100 ng/L 的暴露剂量下，三个抗生素治疗组通常共有两种下调的蛋白质，一种膦酸盐 ABC 转运蛋白和一种甲硫氨酸氨肽酶，以及一种上调的蛋白质，苯丙氨酸-tRNA 连接酶 α 亚基。环丙沙星上调与固氮、碳分解代谢和生物合成相关的蛋白质，但下调与光合作用相关的蛋白质。相反，四环素和磺胺甲恶唑增加了光合活性发菜属 通过上调光合作用相关蛋白质，但下调与固氮、碳分解代谢和生物合成相关的蛋白质。Nostoc sp.的抗性。PCC 7120 对三种目标抗生素的反应与 RNA 合成调节蛋白的反应有关。抗生素污染物刺激蓝藻固氮可能会加剧水生环境中的富营养化。