Genetic diversity of dissolved free extracellular DNA compared to intracellular DNA in wastewater treatment plants

IF 8 1区环境科学与生态学 Q1 ENVIRONMENTAL SCIENCES Science of the Total Environment Pub Date : 2025-03-05 DOI:10.1016/j.scitotenv.2025.178989

Soichiro Tamai , Miki Okuno , Yoshitoshi Ogura , Yoshihiro Suzuki

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Abstract

Dissolved free extracellular DNA (free-exDNA) coexists with intracellular DNA (inDNA) in aquatic environments. Free-exDNA can be taken up by bacteria through transformation, and wastewater treatment plants (WWTPs) are positioned as potential hot spots for genetic contamination. However, studies comparing the composition of free-exDNA and inDNA is limited. This study employed colloidal adsorption and foam concentration method to recover free-exDNA from different WWTP stages and compared its diversity with inDNA via metagenomic analysis. Free-exDNA concentrations were observed to increase after chlorination. Genetic analysis revealed a higher abundance of specific genes following chlorination, suggesting that free-exDNA in effluent originated from bacterial death in secondary treated water. This result indicates that free-exDNA, which increases due to chlorination, is subsequently released into the catchment. Additionally, several high-risk antibiotic-resistance genes (ARGs) were detected that colocalized with mobile genetic elements. These ARGs were expected to have a high potential for gene transfer via transformation, and the risk was highlighted. Overall, these findings deepen our understanding of horizontal gene transfer risks in WWTPs.

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污水处理厂中溶解游离细胞外DNA与细胞内DNA的遗传多样性比较

溶解的游离细胞外DNA （free- exdna）与细胞内DNA （inDNA）在水生环境中共存。游离脱氧核糖核酸（Free-exDNA）可以通过转化被细菌吸收，污水处理厂（WWTPs）被定位为基因污染的潜在热点。然而，比较游离dna和dna组成的研究是有限的。本研究采用胶体吸附和泡沫富集法对不同污水处理阶段的游离exdna进行回收，并通过宏基因组分析比较其与inDNA的多样性。经氯化处理后，游离脱氧核糖核酸（Free-exDNA）浓度升高。遗传分析显示，氯化处理后的特定基因丰度更高，表明出水中的游离dna来自于二次处理水中的细菌死亡。这一结果表明，由于氯化作用而增加的游离dna随后被释放到集水区中。此外，还检测到几种高风险抗生素耐药基因（ARGs）与移动遗传元件共定位。预计这些ARGs通过转化具有很高的基因转移潜力，并强调了风险。总的来说，这些发现加深了我们对污水处理厂水平基因转移风险的理解。

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来源期刊

Science of the Total Environment 环境科学-环境科学

CiteScore

17.60

自引率

10.20%

发文量

8726

审稿时长

2.4 months

期刊介绍： The Science of the Total Environment is an international journal dedicated to scientific research on the environment and its interaction with humanity. It covers a wide range of disciplines and seeks to publish innovative, hypothesis-driven, and impactful research that explores the entire environment, including the atmosphere, lithosphere, hydrosphere, biosphere, and anthroposphere. The journal's updated Aims & Scope emphasizes the importance of interdisciplinary environmental research with broad impact. Priority is given to studies that advance fundamental understanding and explore the interconnectedness of multiple environmental spheres. Field studies are preferred, while laboratory experiments must demonstrate significant methodological advancements or mechanistic insights with direct relevance to the environment.