摘要
      腐殖酸（HA）是一种广泛存在于自然界的有机大分子化合物，但其对镉污染土壤中抗生素抗性基因（ARGs）的影响尚不清楚。本研究调查了土壤中镉（Cd）和HA对ARGs、移动遗传元素（MGEs）和细菌群落的影响。向土壤中添加2 mg kg−1 Cd后，ARGs和MGEs的相对丰度分别增加了0.89倍和1.12倍，添加8 mg kg−2 Cd后分别增加了1.06倍和1.68倍。冗余分析进一步表明，在环境因素中，有效Cd是影响ARGs的主导因素。在镉污染的条件下，高浓度HA的加入抑制了ARGs和MGEs的表达。在镉浓度为2 mg kg−1的土壤中添加HA（50 mg kg−2）后，ARGs和MGEs的丰度分别下降了0.12倍和0.44倍，在镉浓度8 mg kg−3的土壤中分别下降了0.18倍和0.41倍。IntI1与所有ARG（sul1、sul2、tetG、tetW）显著相关，而intI2与大多数ARG（sul2、temG、temW）显著关联。网络分析表明，变形杆菌是导致ARGs和MGEs丰度变化的主要宿主细菌。HA在农业生产中发挥着重要作用。为了减少镉污染土壤中ARGs的富集，可以考虑添加更高浓度的腐殖酸来减轻环境和生物危害。
Abstract
Humic acid (HA) is an organic macromolecular compound that widely exists in nature, but its effect on antibiotic resistance genes (ARGs) in Cd-contaminated soil is unknown. This study investigated the effects of Cadmium (Cd) and HA in soil on ARGs, mobile genetic elements (MGEs), and bacterial communities. The relative abundance of ARGs and MGEs increased 0.89-fold and 1.12-fold after the addition of 2 mg kg−1 Cd to the soil, and 1.06-fold and 1.68-fold after the addition of 8 mg kg−1 Cd. Redundancy analysis further revealed that among environmental factors, available Cd was the dominant factor influencing ARGs. In Cd-contaminated conditions, the addition of high concentrations of HA suppressed the expression of ARGs and MGEs. The abundance of ARGs and MGEs decreased by 0.12-fold and 0.44-fold after the addition of HA (50 mg kg−1) to the soil at a Cd concentration of 2 mg kg−1, and by 0.18-fold and 0.41-fold at a Cd concentration of 8 mg kg−1. IntI1 was significantly associated with all ARGs (sul1, sul2, tetG, tetW), and intI2 was significantly correlated with most ARGs (sul2, tetG, tetW). Network analysis illustrated that Proteobacteria were the main host bacteria causing changes in the abundance of ARGs and MGEs. HA has an important role in agricultural production. To reduce the enrichment of ARGs in Cd-contaminated soil, the addition of higher concentrations of humic acid can be considered to mitigate the environmental and biological hazards.

https://www.sciencedirect.com/science/article/abs/pii/S095758202200101X