The veterinary antibiotic oxytetracycline and Cu influence functional diversity of the soil microbial community

There are increasing concerns over the effects of veterinary antibiotics and heavy metals in agricultural soils. The widely used veterinary antibiotic oxytetracycline (OTC), Cu and their combination on soil microbial community function were assessed with the Biolog method. The microbial community was extracted from the soil and exposed to a 0.85% sodium chloride solution containing OTC (0, 1, 5, 11, 43, 109 and 217 mu M), or Cu (0, 10, 20, 100 and 300 mu M), or combination of the two pollutants (OTC 0, 5, 11 mu M and Cu 0, 20 mu M). Functional diversity, evenness, average well color development (AWCD) and substrate utilization decreased significantly with increasing concentrations of OTC or Cu (p < 0.005). The critical concentrations were 11 mu M for OTC and 20 mu M for Cu. The combination of OTC and Cu significantly decreased.4 Shannon's diversity, evenness and utilization of carbohydrates and carboxylic acids compared to individual one of the contaminants. The antibiotic OTC and Cu had significant negative effects on soil microbial community function, particularly when both pollutants were present. (c) 2005 Elsevier Ltd. All rights reserved.