Long Term Exposure of Agricultural Soil to Veterinary Antibiotics Changes the Population Structure of Symbiotic Nitrogen-Fixing Bacteria Occupying Nodules of Soybeans (Glycine max)

International audience; Antibiotics can be entrained onto agricultural land through the application of animal manures, human biosolids, or recycled wastewater for irrigation. In order to evaluate the impacts on soil microorganisms of exposure to antibiotics, a series of replicated plots were initiated in 1999 at the AAFC research farm in London ON. Every spring a mixture of sulfamethazine, chlortetracycline and tylosin is incorporated directly into the soil to attain concentrations ranging from 0.1 to 10 mg/kg, and these are then seeded with soybeans. In the present study nodules were isolated from soybean plants growing in antibiotic treated and control soils in 2012, after 14 annual treat…