重金屬與菌群結構及抗生素抗性基因於河口底泥的分佈之關聯

Abstract

近年來工業發展迅速，重金屬污染案件層出不窮，已引起社會大眾密切關注。河口底泥為河川長期累積沖刷而成，其做為污染物之儲存庫，對重金屬具有沉澱、吸附與錯合作用使其移動性降低，進而成為潛在重金屬累積之熱點。重金屬污染除了造成環境菌群結構改變外，同時也極有可能是導致環境中的抗生素抗性基因(Antibiotic Resistance Genes, ARGs)傳播之關鍵因素。然而目前針對重金屬對菌群結構的改變及抗生素抗性基因於河口底泥的分佈尚未得到廣泛之研究，有鑑於此，本研究選擇新竹香山濕地及西南沿海一帶做為研究場址，透過採集表層河口底泥，以次世代定序技術分析菌群結構，以及使用即時聚合酶連鎖反應定量分析抗生素抗性基因，最後透過相關性分析找出重金屬與兩者之關聯。結果顯示河口底泥之抗生素抗性基因與Class 1 Integrons及重金屬具有顯著之關聯性，代表水平基因轉移及共選擇機制可能為河口底泥抗生素抗性基因傳播的主要原因。菌群結構部分，PCoA及CCA分析顯示即便重金屬濃度無超過底泥品質指標之分類管理及用途限制辦法之上限值，長期的污染仍然可能導致菌群結構產生變化，其中AB-539-J10、Desulfarculaceae、Hydrogenophilaceae、Marinilabiliaceae、Methanomicrobiaceae、Methanoregulaceae、Methanosaetaceae、SG8-4、Spirochaetaceae、Sulfurovaceae、Synergistaceae等11科菌科與多種重金屬顯著正相關，為河口底泥重金屬污染下之優勢菌科。最後透過網絡分析發現Chloroflexi、Euryarchaeota、Spirochaetes、Tenericutes為抗生素抗性基因與菌門網絡中之熱點，顯示其可能為抗生素抗性基因於河口底泥之潛在宿主。

Industry has developed rapidly in recent years and heavy metal pollution cases have emerged one after another, which has aroused attention from the public. As a reservoir of pollutants, estuary sediments can reduce heavy metals’ mobility due to precipitation, adsorption and complexation. Therefore, they become hotspots of heavy metal pollution. In addition to changing the microbial community structure, heavy metals are also likely to be a critical factor that promote the propagation of antibiotic resistance genes (ARGs). However, impact of heavy metals on the changes in microbial community structure and the distribution of antibiotic resistance genes in estuary sediments have not been studied extensively. In view of this, this study collected surface estuary sediments from Hsinchu Xiangshan Wetland and the southwest coastal area of Taiwan. Microbial community structure was analyzed by next-generation sequencing technology, and abundance of antibiotic resistance genes was analyzed by real-time polymerase chain reaction. Results showed that antibiotic resistance genes had significant correlations with Class 1 Integrons and heavy metals, indicating that horizontal gene transfer and co-selection mechanisms may be the main reasons for the spread of antibiotic resistance genes in estuary sediments. For the microbial community structure, PCoA and CCA analysis showed that even if the heavy metal concentration did not exceed the upper limit of sediment quality regulations, long-term pollution could still change microbial community structure. Among all the families, AB-539-J10, Desulfarculaceae, Hydrogenophilaceae, Marinilabiliaceae, Methanomicrobiaceae, Methanoregulaceae, Methanosaetaceae, SG8-4. Spirochaetaceae, Sulfurovaceae and Synergistaceae had strong and positive correlations with multiple heavy metals, indicating that they are the dominant microorganisms in the estuary sediments under heavy metal pollution. At last, we performed network analysis and found that Chloroflexi, Euryarchaeota, Spirochaetes, and Tenericutes are hotspots in the network of antibiotic resistance genes and phylums, showing that they may be potential hosts for antibiotic resistance genes in estuary sediments.