Effects of veterinary medicines in manure on the abundance and transfer of bacterial antibiotic resistance genes in soil: importance of the rhizosphere and of prepeated manure applications

在本项目的第一阶段，我们发现，施用含抗生素的粪肥可以提高抗生素抗性基因的丰度及其可转移性，并鉴定出一种质粒类型，在粪肥和土壤细菌之间的抗性基因水平传播中起主要作用。在第二阶段，我们的目标是阐明含有兽药的粪肥土壤施肥是否受到根际和重复施用粪肥的影响。这将在土壤中环境和田间试验中进行研究。将在微观环境（A1， C）中进行低时空分辨率的根际效应分析和建模。将在一个中心田间试验的样品中调查反复施用有机肥对散装土壤和根际土壤中抗性种群的积累。利用实时荧光定量PCR技术，将获得总群落dna中耐药基因和质粒丰度的定量数据。这些数据将与土壤中可提取和不可提取的抗生素化合物量有关，以阐明其生物利用度和选择力。我们的目标是鉴定和量化粪便和土壤中抗性质粒的宿主，以便将其栖息地特异性命运和种间质粒转移纳入数学模型(C)。

In the first phase of this project we showed that soil fertilization with manure containing antibiotics enhanced the abundance of antibiotic resistance genes and their transferability, and identified a plasmid type that plays a major role in horizontal spread of resistance genes between manure and soil bacteria. In the second phase we aim to elucidate if the effects of soil fertilization with manure containing veterinary medicines are influenced by the rhizosphere and by repeated application of manure. This will be investigated in joint soil mesocosm and field experiments. Analysis and modeling of rhizophere effects at a low spatial and temporal resolution will be performed in microcosms (with A1, C). Accumulation of resistant populations in bulk and rhizosphere soil by repeated manure application will be investigated in samples from a central field experiment. Quantitative data on the abundance of resistance genes and plasmids in total community (TC)-DNA will be obtained by real time PCR. These data will be related to extractable and non-extractable amounts of antibiotic compound in soil to clarify their bioavailability and selective force. We aim to identify and quantify the hosts of resistance plasmids in manure and soil, in order to incorporate their habitat-specific fate and inter-species plasmid transfer into a mathematical model (C).