导读 | Introduction
Antibiotics are widely used in the prevention or treatment of human and animal diseases. Antibiotic resistance has become a serious threat to global public health. Animal manure is routinely applied to the land as fertilizer. Manure application have been documented to increase soil antibiotic resistance genes (ARGs), accumulation and persistence of ARGs in agricultural soils is a growing concern. Our previous studies demonstrated that 79 types of ARGs and various antibiotics were found at different soil depth of 0-70 cm, suggesting accumulation of ARGs in crop fields. To provide basis data for agricultural use of organic fertilizer, this study used soil microcosms to evaluate the impact of field moistures and biochar on the fate of ARGs.
一、耐药基因丰度与细菌生物量的动态变化 | Dynamic change of of ARGs and bacterial biomass
常年施肥土壤和对照土壤的16S rRNA基因丰度在8.5×10-9–1.12×10-11 copies/g之间（图1）。常年施肥的土壤细菌生物量与对照组相当，有的甚至显著低于对照组。然而，施肥处理土壤耐药基因的总丰度显著高于对照土壤。
The abundance of 16S rRNA gene in both manure-applied and control treatments ranged between 8.5×10-9–1.12×10-11 copies/g dry weight of soil (Fig.1). Manure-amended soil had as much bacterial biomass as or even significantly less than those control treatments. However, the total abundance of target ARGs in manure-soils were significantly higher than those in control treatments.
图1 耐药基因和16S rRNA基因总丰度的动态变化
土壤耐药基因丰度和细菌生物量在两年内均随时间呈现出逐渐下降的趋势（图2）。其中，耐药基因总丰度从109减少至107或108copies/g。在730天时，耐药基因在添加生物质炭的土壤中的平均丰度减少至1.52 ×108±7.00 ×106copies/g，但仍然显著高于相应的对照处理组，表明生物质炭促进耐药基因在土壤中的持留。
After two years' incubation, both ARGs and bacterial biomass declined gradually with time (Fig.2). Total abundance of ARGs in these four treatments declined from 109 to 107 or 108 copies/g dw. At the end of our experiment (day 730), total concentration of ARGs in biochar-amended soils decreased to 1.52×108±7.00× 106 copies/g dw, but still higher than those in control treatments.
Fig. 2. Abundance and diversity of target ARGs in manure-applied soils.
二、细菌群落结构及其多样性特征 | Structure and diversity of microbial community
Fig. 3. Structure and diversity of microbial community during soil incubation.
三、水分与生物质炭的添加对土壤耐药基因消散的影响 | Effect of moisture and biochar on the dissipation of soil ARGs
The fate of ARGs in soils received continuous manure application was different to that in control soils (Fig.4a). Soil moisture and biochar had significant impact on the fate of soil ARGs and microbial community. (Fig.4b and c) .
Fig. 4. Effect of moisture and biochar on the fate of target ARGs in soil treatments within two years.
总结 | Conclusions
Continuous manure application induced an accumulation of ARGs into soil, wherein abundance of ARGs declined by one or two order of magnitude within two years. ARGs dissipated more slowly in 20% moisture soil or biochar-amended soil. Overall, biochar amendment contributed to maintain bacterial diversity, sustain ARGs and delay their dissipation in soil. The results provide important data for the risk assessment of manure application and soil ARGs.
本文内容来自ELSEVIER旗舰期刊Sci Total Environ第787卷发表的论文：
He, L. Y., et al., Dissipation of antibiotic resistance genes in manure-amended agricultural soil. Science of The Total Environment 2021, 787: 147582.