College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China; Center for Microbial Ecology, Michigan State University, East Lansing, MI 48824, USA.
College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China.
Sci Total Environ. 2019 Jul 15;674:383-391. doi: 10.1016/j.scitotenv.2019.04.197. Epub 2019 Apr 14.
Due to the intensive use of feed additives in livestock farming, animal manure has become a hotspot for antibiotics, heavy metals, and antibiotic resistance genes (ARGs). Unlike antibiotics, heavy metals cannot be degraded during composting and thus could pose a persistent co-selective pressure in the proliferation of antibiotic resistance. Passivators are commonly applied to immobilize metals and improve the safety of compost. However, little is known about the effects of various passivators on ARGs and mobile genetic elements (MGEs) during composting and the underlying mechanisms involved. Thus, three typical passivators (biochar, fly ash, and zeolite) were applied during the composting of copper-enriched pig manure, and their effects on ARGs, copper resistance genes, MGEs, and the bacterial communities were examined. Compared to the control, all passivator treatments reduced the abundances of at least six ARGs (tetC, tetG, tetQ, tetX, sul1, and ermB) by 0.23-1.09 logs and of two MGEs (intI1 and ISCR1) by 26-85% after composting. Biochar and fly ash also significantly reduced the abundances of intI2 and Tn914/1545. In contrast, abundances of copper resistance genes were not reduced by passivators, implying that the decreased co-selective pressure may not be a major contributor to ARG reductions in this study. Procrustes analysis and redundancy analysis demonstrated that shifts in the bacterial community determined the changes in the abundances of ARGs, and the variation in MGEs and DTPA-Cu can also partially explain the ARG variance. Overall, all of three passivators can be used to reduce the health risks associated with ARGs in livestock manure, and biochar performed the best at reducing ARGs and MGEs.
由于在畜牧业中大量使用饲料添加剂，动物粪便已成为抗生素、重金属和抗生素抗性基因（ARGs）的热点。与抗生素不同，重金属在堆肥过程中不会降解，因此可能会对抗生素抗性的增殖产生持续的共选择性压力。钝化剂通常用于固定金属并提高堆肥的安全性。然而，人们对各种钝化剂在堆肥过程中对 ARGs 和可移动遗传元件（MGEs）的影响及其潜在机制知之甚少。因此，在富铜猪粪堆肥过程中应用了三种典型的钝化剂（生物炭、粉煤灰和沸石），并考察了它们对 ARGs、铜抗性基因、MGEs 和细菌群落的影响。与对照相比，所有钝化剂处理均使至少六种 ARGs（tetC、tetG、tetQ、tetX、sul1 和 ermB）的丰度降低了 0.23-1.09 个对数，两种 MGEs（intI1 和 ISCR1）的丰度降低了 26-85%。生物炭和粉煤灰还显著降低了 intI2 和 Tn914/1545 的丰度。相比之下，铜抗性基因的丰度未被钝化剂降低，这表明降低的共选择性压力可能不是本研究中 ARG 减少的主要原因。普罗克汝斯分析和冗余分析表明，细菌群落的变化决定了 ARGs 的丰度变化，而 MGEs 和 DTPA-Cu 的变化也可以部分解释 ARG 的变化。总体而言，三种钝化剂均可用于降低牲畜粪便中与 ARGs 相关的健康风险，其中生物炭在降低 ARGs 和 MGEs 方面表现最佳。
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