Effects of veterinary medicines in manure on the abundance and transfer of bacterial antibiotic resistance genes in soils in dependence of varying soil moisture conditions

B3研究表明，在两种不同土壤中，重复施用含磺胺嘧啶（SDZ）粪肥，抗性基因（sul1、sul2）拷贝数较不施用或对照显著增加，并随着重复施用而积累。在田间条件下，猪粪对SDZ抗性的可转移性显著提高。根际土壤的转移频率高于散装土壤。不同取样时间，含sdz肥料对玉米和草根际sul基因丰度的影响可能与气候因素有关。我们假设干燥和再湿润引起养分有效性、植物渗出物和生物可达孔隙空间的变化，这些变化影响SDZ对土壤微生物群落中抗性基因丰度和转移的影响。为了阐明干燥-再湿润和温度的影响，并澄清这一缺失的环节，我们将从中心田的草根际和根际取样，并通过操纵干湿循环的实验室实验，研究sul基因的丰度及其可转移性。粪便处理土壤中可转移抗性组的焦磷酸测序将为SDZ共同选择的质粒多样性和其他抗生素抗性基因提供独特的见解。

Research of B3 revealed that in two different soils repeatedly treated with sulfadiazine (SDZ)-containing manure, resistance gene (sul1, sul2) copies significantly increased compared to treatments with antibiotic-free manure or control, and accumulated with repeated applications. Under field conditions, the transferability of SDZ resistance was significantly increased in plots treated with manure originating from pigs medicated with SDZ. Transfer frequencies were higher in the rhizosphere compared to bulk soil. The effects of SDZ-containing manure on the abundance of sul genes in the rhizosphere of maize and grass varied between different sampling times supposedly due to climatic factors. We hypothesize that drying and re-wetting cause shifts of nutrient availability, plant exudation and bio accessible pore space, and that these shifts influence the effects of SDZ on abundance and transfer of resistance genes in soil microbial communities. In order to elucidate the effects of drying-rewetting and temperature and to clarify this missing link, the abundance of sul genes and their transferability will be investigated in samples taken from rhizosphere and rhizoplane of grass from the central field and laboratory experiments with manipulated drying and wetting cycles. Pyrosequencing of the transferable resistome in manure-treated soils will provide unique insights into plasmid diversity and other antibiotic resistance genes co-selected by SDZ.