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活性污泥法是目前世界上应用最成功的生物处理技术[1],在水环境保护和公共卫生保障中发挥着重要作用。活性污泥法以细菌群落为主体,含有的细菌种类繁多[2],但又不是细菌细胞的简单聚集,而是不同细菌相互合作形成的具有复杂物理结构的絮体菌胶团[3],从而保证了降解菌在处理系统中的持留和碳、氮、磷等污染物的高效去除[4]。值得注意的是,上述组成复杂的活性污泥微生物群落是由进水及环境中分散的细菌聚集、增殖和相互作用形成的[5-6],解析该形成过程中细菌群落的演替及其对运行参数或环境压力的响应对于深入理解活性污泥降解污染物的微生态机制具有重要指导意义。
李培睿等[7]将活性污泥形成的宏观过程分为4个阶段:细菌增殖阶段、絮状体形成阶段、絮状体聚合阶段和凝絮体形成阶段,其中初期的细菌增殖阶段决定了活性污泥最终的细菌群落组成,对活性污泥微生物群落构建至关重要。李培睿等[7]使用光学和扫描电子显微镜观察发现,活性污泥形成初期以球状游离细菌为主,后期杆菌和丝状菌大量增殖并逐渐形成菌胶团,表明活性污泥初期增殖阶段有明显的微生物群落演替。在群落构建的影响因素方面, GAO等[8]发现初始菌种比例可以改变细菌之间的相互作用关系,从而影响细菌群落的结构和功能。RATZKE等[9]发现高营养条件会促进细菌间的竞争,导致群落多样性降低,进而降低最终群落的稳定性。除了接种比例和营养水平外,环境压力也是影响活性污泥细菌群落构建的一个关键因素[6]。随着抗生素的广泛使用,环境水体中抗生素检出频率和浓度均逐渐有所增加[10-12],在畜禽养殖、医院和制药等污水中抗生素质量浓度甚至可达到mg·L−1[13-17],使得抗生素类药物成为一种潜在影响活性污泥形成过程的环境压力。抗生素如四环素和诺氟沙星等在低浓度时具有信号分子的作用,可以促进细菌的移动和聚集[18]。低浓度四环素还可选择性富集硝化细菌和聚磷菌[19],进而有可能促进活性污泥的形成。而高浓度抗生素具有抑菌和杀菌作用,可显著抑制硝化菌和反硝化菌增殖[19],并可导致活性污泥解体[20]。因此,抗生素在不同的浓度水平下可能会对活性污泥微生物群落的构建过程产生不同的影响,但相关研究还未见报道。
本研究选择了中国使用量大的第2代四环素米诺环素作为模型化合物[21],设置无抗生素暴露对照组和5个抗生素浓度梯度,通过宏观观测和微生物群落解析,考察了不同抗生素暴露压力下活性污泥初期增殖阶段细菌群落的构建过程及其微生态机制。本研究结果可为含抗生素废水的高效生化处理提供参考。
米诺环素对活性污泥初期增殖阶段的影响
Impact of minocycline on the initial formation of activated sludge
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摘要: 采用污泥连续培养的方式,分别考察了米诺环素在质量浓度为0、0.001、0.01、0.1、1和10 mg·L−1水平下对活性污泥初期增殖阶段的影响。结果表明,各组污泥增殖均能在20 d内进入平台期,且组间的稳态污泥量差异不显著 (P>0.05),表明活性污泥宏观生物量的增长与米诺环素浓度无关,但10 mg·L−1米诺环素的暴露可抑制污泥絮体的形成。细菌群落多样性的分析结果表明,1 mg·L−1的米诺环素即可导致活性污泥初期增殖阶段细菌多样性的降低,10 mg·L−1的米诺环素会选择性富集Flavobacterium菌属,使其丰度在第20天的活性污泥细菌群落中达到83.14%,可进一步降低形成的活性污泥细菌多样性。网络分析结果表明,Proteobacteria细菌是活性污泥初期增殖阶段的关键物种,低质量浓度米诺环素(0.001 mg·L−1和0.01 mg·L−1)可能促进了活性污泥细菌间的互作,而高质量浓度(1 mg·L−1和10 mg·L−1)暴露会显著降低互作网络的复杂度和稳定性。本研究结果可为含抗生素废水的高效生化处理提供参考。Abstract: Activated sludge (AS) was continuously incubated at the mass minocycline concentrations of 0, 0.001, 0.01, 0.1, 1 and 10 mg·L−1, respectively, and the effects of these concentrations on the initial formation of AS were investigated. The results showed that the biomass proliferation in 0~10 mg·L−1 minocycline treatments all entered the plateau stage within 20 days, and there were no significant differences (P> 0.05) in the steady-state sludge concentrations among the treatments, indicating that the growth of AS biomass was not delayed by the addition of minocycline, but the exposure of 10 mg·L−1 minocycline could lead to the failure of the formation of AS flocs. Miseq sequencing of 16S rRNA gene amplicons showed that the bacterial diversity of AS at its initial proliferation stage decreased in 1 mg·L−1 minocycline treatment, and 10 mg·L−1 minocycline exposure selectively enriched the genus Flavobacterium, and its abundance could reach 83.14% in the AS bacterial community at the end of the experiment, then the diversity of the formed AS bacterial community was further reduced. Network analysis showed that members of Proteobacteria were the key players in the initial formation of AS. Low mass concentration minocycline (0.001 and 0.01 mg·L−1) might promote the interaction between different modules of AS bacterial communities, while high mass concentration (1 and 10 mg·L−1) exposure would significantly reduce the complexity and stability of AS network. The results of the study can provide a reference for the efficient biochemical treatment of antibiotic-containing wastewater.
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Key words:
- minocycline /
- activated sludge /
- proliferation /
- community construction /
- network analysis
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表 1 网络关键物种解析
Table 1. Key players during the initial formation of activated sludge revealed by network analysis
抗生素暴露
浓度/(mg·L−1)网络分析揭示的关键物种 网络中心点 模块中心点 连接节点 OTU Genus OTU Genus OTU/个 0 — — 2 889 norank_f__norank_o__PLTA13 10 432 Shinella 1 963 Paenarthrobacter 1 069 Propionicicella 0.001 — — 2 926 Hydrogenophaga 71 2 889 norank_f__norank _o__PLTA13 3 203 norank_f__A4b 0.01 3 142 Hyphomicrobium 4 820 Comamonas 51 794 unclassified_f_Burkholderiaceae 1 639 Pseudoxanth omonas 4 437 Comamonas 0.1 — – 1 639 Pseudoxanthomonas — 1 208 Leucobacter 775 unclassified_f__ Burkholderiaceae 613 unclassified_f__ Burkholderiaceae 1 — — 604 Brevundimonas — 1 — — 432 Shinella — 2 944 Acinetobacter 4 467 Sphingobacterium 3 142 Hyphomicrobium 4 863 Fluviicola 10 — — 4 349 Rheinheimera 2 注:*连接节点仅展示了OTU的总数量;其它节点仅展示OTU编号及所属分类;“–”代表无相关OTU。 -
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