Brandt Kristian K, Sjøholm Ole R, Krogh Kristine A, Halling-Sørensen Bent, Nybroe Ole
Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
Environ Sci Technol. 2009 Apr 15;43(8):2963-8. doi: 10.1021/es803546y.
Sulfadiazine (SDZ) residues constitute an important pollutant in soils that may increase environmental reservoirs of antibiotic resistance. Our primary aim was to compare the development of pollution-induced community tolerance (PICT) to SDZ concentration levels in bulk soil and nutrient amended soil hotspots. Agricultural soil microcosms were amended with different concentrations of SDZ with or without weekly additions of artificial root exudates corresponding to realistic rhizodeposition rates. Bacterial community tolerance to SDZ residues, as determined by the [3H]leucine incorporation technique, increased progressively with elevated SDZ exposure, and was significantly increased in soil hotspots (LOEC of 1microg kg(-1)). An alternative PICT approach based on single-cell esterase probing by flow cytometry failed to demonstrate SDZ impacts. Bacterial growth rates ([3H]leucine incorporation) were significantly reduced in both bulk soil and hotspots 24 h after amendment with environmentally relevant concentrations of SDZ, while soil respiration remained unaffected even at 100 microg SDZ g(-1). Our study for the first time demonstrates a drastically increased PICT response of a soil bacterial community due to increased carbon substrate amendment per se. Hence, hotspot soil environments such as rhizosphere and manure-soil interfaces may comprise key sites for proliferation of bacteria that are resistant or tolerant to antibiotics.
磺胺嘧啶（SDZ）残留是土壤中的一种重要污染物，可能会增加抗生素抗性的环境储存库。我们的主要目的是比较污染诱导群落耐受性（PICT）在整块土壤和添加养分的土壤热点中对SDZ浓度水平的发展情况。农业土壤微观模型用不同浓度的SDZ进行处理，添加或不添加对应实际根际沉积速率的人工根系分泌物。通过[3H]亮氨酸掺入技术测定，细菌群落对SDZ残留的耐受性随着SDZ暴露量的增加而逐渐提高，并且在土壤热点中显著增加（最低观察效应浓度为1微克/千克）。基于流式细胞术单细胞酯酶探测的另一种PICT方法未能证明SDZ的影响。在用与环境相关浓度的SDZ处理后24小时，整块土壤和热点中的细菌生长速率（[3H]亮氨酸掺入）均显著降低，而即使在100微克SDZ/克的情况下，土壤呼吸仍未受影响。我们的研究首次证明，由于碳底物添加量本身的增加，土壤细菌群落的PICT反应大幅增强。因此，根际和粪肥-土壤界面等热点土壤环境可能是对抗生素具有抗性或耐受性的细菌增殖的关键场所。
